I'm not knowledgable of mobile services in the UK but I would definitely recommend looking into a Vonage phone. A few friends/families of mine have it. Basically the idea is that, say your whole family lives in Seattle, you can get a number from that area so that it will remain a local call for them. Wherever you move, you bring the Vonage phone and keep that Seattle (or wherever you choose) number with you and they have decent rates. I have a friend from Washington and she now lives in Japan but we still call her Washington number to reach her.
So maybe you can get your child the phone/equipment necessary for your local town.
Check out their
site here for the rates, availability, and how the whole process works. Now I'm not sure if there are any "cell phone" capabilities, but as long as you're home then you can always make that phone call or your child can call home. I do see on the site a call forwarding feature...that may be something to look into as well.
I hope this helps!
