So much for a summer digital detox. The average person spends 40 minutes a day glued to the internet on their smartphone while on holiday. Those aged 25 to 34 spend on average an hour, according to research by iD, a new mobile network that has released free roaming deals to all customers to meet the growing demand to be ?constantly connected?.

It is our desire to tweet and post pictures on Facebook and Instagram of the hotel?s infinity pool, or our tanned hot-dog legs on a sun lounger, that is to blame, as most people admit that their social media addiction is driving a compulsion to roam.

At the beginning of this month the EU voted to scrap roaming charges altogether from summer 2017.

However, campaigners warn that the move is a long way off, and in the meantime thousands are still experiencing bill shock through a lack of understanding of how much data they use overseas, or the multitude of complicated charges applied by networks.

It was reported this week that a 19-year-old NHS worker ran up a ?21,819 phone bill with O2 during a two-week family holiday to Turkey after using FaceTime and Facebook.

Ernest Doku, a telecoms expert for uSwitch.com, says a fifth of UK holidaymakers have returned home from an EU trip in the past year to a bill that is, on average, ?61 higher than usual. If you travel outside the EU ? and it?s worth remembering that some European countries such as Turkey will not be part of the data-capping agreement ? you will still face sky-high costs for using your smartphone to roam.

Networks are, however, responding to demand and offering low-cost deals for those who want to use their UK data, minutes or text allowance overseas.

Here?s what you need to know before you start hashtagging your summer holidays:

The best deals

The mobile operator Three is generally considered the best provider for those who want to access the internet on their phone abroad, says Duncan Heaney, of the comparison site www.mobilechoices.co.uk.

Three?s Feel at Home plan allows you to eat through your normal allowance of minutes, texts and data at no extra cost in up to 18 countries. These include Ireland, France, Italy, Spain, Scandinavia, and, further afield in Australia and New Zealand, the USA and Hong Kong.

Worth noting, however, is that you only get 3G data access, and it is capped, even if you have ?unlimited? plans in the UK, albeit at a generous rate of 5,000 texts and 25GB of data. Also, you only get UK-rate calls for phoning UK numbers; you?ll be charged roaming rates for foreign numbers, for example, if you call a local restaurant to book a table.

ID Mobile, owned by Carphone Warehouse and running on the Three network, launched in May offering free roaming charges.

A spokesman for the company says that it listened to customers? feedback on what was important when looking for a new mobile provider.

?Bill shock and unexpected roaming charges came top of the list,? he says.

?People are keen to stay connected to friends and family while they are away ? they post more pictures and check social media more than ever before, even when in another country.?

ID ?Takeaway? plans, which start from ?25.50 a month on a 24-month contract, include access to free roaming in 22 countries, most of which are in Europe, such as France, Germany, Spain, Greece, Italy, the Netherlands and Portugal, plus Australia and the USA.

Both Three and ID offer sim-only deals, some of which are on one-month rolling contracts, which, if you don?t need a new handset, work out much cheaper than signing up to a 24-month contract.

The rest

Vodafone, EE and O2 have ?opt in? bundles. Vodafone?s is the best value, says Mr Doku, at ?3 per day for the Euro Traveller option, which gives you access to your full UK calls, minutes and data allowance overseas. World Traveller, for countries outside the EU, costs ?5 a day. Vodafone also enables you to surf on the speedier 4G network.

Do check that your holiday destination is in its ?applicable zones?, though. World Traveller functions in quite a few, including South Africa, India, the USA, Australia, New Zealand and the Caribbean.

EE customers are not allowed to use data abroad unless they buy a bundle. Pay monthly and pay-as-you-go customers can pay an extra ?3 a day for a 50MB daily allowance in the EU, ?5 for 100MB, or ?12 for 200MB to be used over seven days.

EE?s Euro Talk and Text plan costs ?2 for unlimited amounts of both, and the benefit is that you can call foreign numbers as well as UK numbers.

If you are travelling beyond Europe you can pay for separate minutes or text bundles ? ?6 a month for 100 texts or the same price for 30 minutes of calls.

O2 customers can have ?O2 Travel? added free to their account, which means you can make and receive calls between a selection of European countries for a connection charge of 50p, after which it?s free to talk for up to an hour. It also charges ?1.99 a day for using data in most of Europe, with no upper limit. Pay & Go customers can buy

50MB of data per day for ?1.99. But O2 doesn?t offer any bundles for mobile use outside Europe.

Beware the ?data caps?

In theory all networks have a ?50 data cap, at which point they must alert customers to their imminent overspending, whether they are roaming inside or outside the EU, though Times Money has seen many examples of people who have failed to receive this alert.

Be aware, however, that as soon as you opt in to a data package, such as Vodafone?s World Traveller, or O2?s Travel package, you are automatically opting out of the ?50 data cap. Your network may not be quick to draw this to your attention. If you then go over your data limit you will be paying full foreign fees to surf the web, and can expect a hefty bill on the doormat on your return that could be for thousands of pounds.

How to get around roaming charges

Download a map of the local area using a wi-fi hotspot at your holiday location, and the map data will be stored on your device. The GPS function will work as normal even when you have turned mobile data off.

To make free calls Mr Doku recommends downloading one of a number of apps available from the networks, such as Smartcall from Virgin, TuGo on O2 and Three?s InTouch, which will reroute traditional calls, and sometimes texts, over wi-fi, taking them out of your UK bundle. You can also use apps such as Viber, Whatsapp and Skype.

The costs

Within the EU most networks charge a similar fee for calls, texts and data because costs are capped. At the moment, this works out at an average of 17p per MB for data, about 5p per text message, about 16p to make a call per minute, and 4p per minute to receive one.

It is a different story outside the EU. EE charges ?1.50 per minute to make or receive a call in India, and O2 charges ?6 per MB to roam in Australia, the US or Turkey.

As a guide to how much data you need, Vodafone has a useful tool on its website. According to its calculations, reading and sending 15 emails a day would use about 1MB of data, as would three posts on social media, or looking at one web page or app per day. Streaming ten minutes of music on an app such as Spotify eats about 7MB and ten minutes of video, a massive 38MB.

?When abroad I use my phone for four hours a day?

Carlly Chun, 24, right, is a typical smartphone user reliant on mobile internet at home and abroad ? both for work, socialising and travel information.

She goes abroad every few months, and says she uses her phone ?two to four hours a day? to check social media and send messages and emails.

?A lot of the places I go to don?t always have a wi-fi caf?, and often it makes sense to have the internet while I?m out and about. More than once I have been saved from getting lost by paying extra for roaming.

?I use Vodafone ?EuroTraveller? pay as you go. I usually use Talk Mobile but have a spare Vodafone sim if I go abroad. I usually buy a roaming bundle. It is about ?3 a day with a cap of 100MB, which sounds a lot, but I download a lot on Spotify and can run out by the evening. I?d prefer to have fast 4G.?