SIM card for Android phone in England

I'll plug Giffgaff as I always do,been with them 8 years.
Register SIM online ,buy a goody bag package and away you go
Pretty much most phones work immediately.
That said was in carphone warehouse and they now have thier own network ( well actually 3's ) they piggy back and is a couple of quid cheaper than giffgaff.
The monthly deals are way better value than pay as you go,I doubt you need to spend more than 30 bucks to get all data and calls you could ever need.If you have two phones as long as you choose same network it's almost certain to be free calls between them.
I always give my visting US cousins phones and Sims as thier US carrier was charging them 69 cents per minute and the out going and incoming call !

I have been researching the same question for an upcoming trip to England. Any card you buy in England will be a UK card, i. e., that includes England, Wales, Scotland and Northern Ireland. As long as the UK is still in the EU, there will be no roaming charges in any other EU country. So, even if you take a quick trip across the Channel to France your SIM card purchased in the UK will work fine.
I plan on buying my SIM card at a Carphone Warehouse. They have a selection of cards from most of phone companies in the UK. Just google "Carphone Warehouse" and you will be able to find a location near where you will be the first day. Also, you will be able to review their inventory. They were very quick to answer the questions I sent them by email. For me, they have a store just outside London Victoria Station where I am catching a train on my first day.

hmm not sure that giffgaff will work - you'll need a UK address so they can post the SIM.

As said, just find a Carphone Warehouse. The major carriers are EE, Vodaphone, Three and O2, but supermarkets like Tesco and Asda do PAYG SIMS as well.

I need advice, based on your experiences, about buying and using a SIM card on an Android phone in England. What kind of shop is best for price, advice and installation? Is there anything tricky about getting the right card for ones phone? Any brands or carriers that are better than others?

First of all, your US phones must be unlocked. I assume they are not on T-Mobile or Sprint given that those two carriers provide free unlimited data (2G) on their international roaming plans. Verizon phones generally are not locked, but AT&T phones still not paid off probably are; if the AT&T phone is paid off, ask AT&T to unlock it for you.

There are three different sizes of SIM cards, but most prepaid SIM cards now are "3-in-1" which can be broken down to fit any size. If you buy the SIM at a mobile store where someone can help you instead of just buying one at the grocery store, you'll probably have an easier time getting it to work.

Just to be clear: when you insert the UK SIM, you'll have a UK phone number and won't have your US phone number anymore until you put your old SIM back. So no calls or text messages to your US number. For free texting, you can install something like WhatsApp. If you need to make voice calls home to the US, install Google Hangouts (plus Hangouts Dialer if you have an Android), so you can within the app make free calls to US numbers (even landlines) - just add a +1 to the front of the US number to call it (handy to be able to call your airline or credit card company or whatever from Europe and not worry about being on hold for a while, because it's free). You can call non-US numbers with Hangouts too but it's not free - costs a few cents per minute. Hangouts will work on WiFi or with mobile data from the SIM.

If you will be driving, consider downloading the map data "offline" ahead of time to save data - GPS on a phone can work without any mobile data, but you must download the map ahead of time on WiFi. Google Maps has an "offline" mode if you use it - try it out. If you will have plenty of data on the SIM then you probably need not worry about this, though.

Thanks everybody for your replies. Good information, much appreciated.

I bought a Lebara Mobile sim card from a newsstand in Sloane Square in London. Ten pounds got one gig. I texted and talked away fine both inside UK and to the States. You get your own unique UK phone number. It was easy to recharge with another one gig using email.
I went to a Carphone location on Kings Rd. and they didn't have any sim cards. The clerk directed me to a Boots (pharmacy) store.

I’m currently using a Tesco SIM card and they installed it for me at the Tesco store I bought it at. Lots of texts and phone calls and 3 GB of data for £10. It’s working good. If you need to top it up - find a Tesco and buy a voucher for more data and call the number and it loads it up for you. Pretty slick.