We had a good experience with giffgaff phone service in England. We were able to get our UK phone number before we left home and it was cheap.
– We have an unlocked GSM smartphone.
– We requested a free giffgaff SIM via the web at http://giffgaffgsimabroad.wufoo.com/forms/get-a-free-giffgaff-sim-abroad/
– After the SIM card arrived, I created a giffgaff account online. (I had to give them a UK street address. I used the address of where we would be staying. )
– We swapped out the SIM card and followed the instructions to activate the phone. (Then we put the U.S. SIM back in the phone.)
– I purchased a goodybag £12, which gave us 250 UK minutes, unlimited UK texts and unlimited Internet for one month. I was able to use my U.S. credit card to purchase the goodybag online.
When we arrived in the UK, we put the giffgaff SIM card in our phone and we were good to go. We liked being able to give people our phone number before we left home. For £12 we had unlimited internet, which enabled us to use Google Maps, etc. When I activated the account, we received a £5 credit. We were able to make a few phone calls home at the rate of 8p per minute.