Smartphones are invaluable when travelling, stay connected while in the UK
There are a number of options for using your mobile phone (cell phone) here in the UK.
Use wifi only, this won't be so difficult as your accommodation will probably have it and there are many places including buses, trains, cafes and restaurants that will have free wifi. It does of course mean that you can't access your phone on the go all the time and requires some forwards planning. It also means you can't use your phone to make calls to accommodation, restaurants etc. If you do this, make sure you turn data roaming OFF in the phone settings if you are leaving the SIM card in place so you don't get hit with charges for it (remember to turn it back on again when you get back home).
You might already be covered for use in other countries by your phone service provider, so the first step is to check if this is the case. This may be the best option if you already live in the EU, legislation introduced in 2017 allows mobile phone users to "Roam Like at Home" without incurring large additional costs.
If you are arriving in the UK from outside of the EU, you may still be able to use your phone as you do at home, though the chances are the roaming data charges will be more expensive, possibly prohibitively so, again check with your provider and in particular ask how much it will cost to use your phone as you do at home, not just whether you can or not. Following the shock at the cost, plan to buy a SIM card in the UK so you can use your phone for less than the cost of bringing your friends and family with you.
How do I know if my phone is unlocked?
It is more likely in general that your phone is UN-locked already than locked, unlocked phones are sometimes known as "SIM free", this will almost certainly be the case if you bought your phone brand new. Your phone may be "locked" to a particular network if it is part of the contract you have with that network, this is how you get an expensive phone for no upfront fee, the network recoup the cost of the phone over the period of the contract.
To find out if your phone is locked, refer to your contract or call the provider and ask, if it is, then request that it be unlocked, there may be a fee for this.
Where should I buy a SIM card in the UK?
Not at the airport! It might be convenient to do so, but you'll be paying about £10 for something that is widely available for about 99p or even less. There are many high street shops that will sell SIM cards including mobile phone shops, convenience stores and supermarkets.
What kind of deal will I get?
You won't be able to get a monthly contract if you are not a UK resident, though Pay As You Go will be more than enough for the majority of people for a typical tourist visit. Specify this is what you want the SIM card for and then buy a data bundle that will include an amount of phone minutes, a number of text messages and an amount of data transfer. For example, at the time of writing (July 2018) , these are typical deals are available on the UK high street.
You will get a UK phone number with the SIM card which will begin 07, if someone outside of the UK wants to call this number, they need to replace 07 with 44, it may cost you to receive international calls, check when buying if this is important. Your purchased allowances will last for up to 30 days, if you use them up in this time, you will need to top-up again, if you don't use it all in the 30 days, you lose it and you need to top-up to continue using the phone with that SIM card.
To top-up, you will need to buy a card from a shop for the appropriate top-up amount of the network the SIM is on and use the code. Most networks won't allow the use of a non-UK registered credit or bank card to top up over the phone.
Can I use the SIM card anywhere else other than the UK?
Thanks to EU "Roam Like at Home" legislation from 2017, you will be able to use your UK purchased SIM card and data allocation across the EU wherever there is a signal.
Will my phone work in the UK?
All iPhones and the great majority of Android smartphones will work worldwide and so will be fine with UK frequencies. You can check here, if you aren't sure of your phone name and model number, you should find it in the "Settings" under "About phone" or similar.
Can I get a SIM card sent to me before I arrive in the UK?
Yes, there are options to do this, giffgaff will send a free SIM card overseas which can then be topped up with their data packages, there's also a WorldSIM that you can have sent to you in advance that is preloaded with £20 of credit (at a cost of errrr.... £20).