SIM Cards in Great Britian

I looked into this a year ago. At that time Carphone Warehouse (and possibly others) had coverage for the entire UK. However, this did not extend to Ireland (i.e., Republic of Ireland). If you're going to be in the UK including Northern Ireland, the one SIM card should be fine. If you need to use the phone in Ireland, though, you'll need a SIM for Ireland.

That was a year ago so you'd want to double-check.

I'm planning to look into plans by Three when I get to London later this year. It looks like their advanced plans offer roaming in other countries.

http://www.three.co.uk/Store/SIM/Plansforphones#?contract=1&data=1&minutes=&type=alltype

"all the countries in Great Britain (i.e., Scotland, Ireland, and England)"

Be very careful ( when you're Ireland) to NOT mention that you think it's in Great Britain!!!

One sim will cover you for the country that is the United Kingdom of Great Britain and Northern Ireland. This includes England, Scotland, Wales and Northern Ireland.

The Republic of Ireland is an entirely separate country with a different currency and no doubt you'll need a different SIM card there.

Whenever I've traveled western Europe and researched SIMs, I've seen plans that had cheap roaming rates for European travel. The O2 SIM I purchased in the UK a couple years ago had an option for cheap roaming for voice, texts and data. As most European telecoms use GSM networks, roaming is pretty simple and usually cheap...

I have bought a card from a site called SIMCorner that worked in both the U.K. and Ireland. It was only about $35 USD and also had unlimited data. Definitely worth it!