Mobile services -- not sure where else to put this

I'd love to hear advice and recommendations on SIM cards, data plans.  I was looking at the three.co.uk website and it looked like they had some very interesting plans.  Thoughts?  Also, where do we go to get SIM cards?  We'll like keep our T-mobile service from the US for a week or so, until we navigate our way around the UK mobile service world.

One consideration is that three has a deal where you can use your phone as if you were in the UK in a bunch of different countries, including the US.  This makes a huge difference on visits home.  Now EU law has stopped them from ripping us off when in Europe so they are all mostly the same there. 

I use Giff gaff for the whole family and it works fine.  Make a request on the site and they send the SIM immediately.  It's cheap, like £10 per month because it's internet only. 

Otherwise, if you go into a Tesco or Carphone Warehouse, they act like an agent for a bunch of providers and can help you choose.  Be careful, there are so many ways you can be ripped off. 

My wife used Three a while ago and hated them. They may be better now, but I don't know.

I've used EE, O2, and Plusnet, and I've been happiest with EE and Plusnet. Plusnet has the cheapest plans I've found, and they use EE's network, and I've rarely had a problem with coverage.

As Jimbo says, Carphone Warehouse can help point you in the right direction. In my experience, it helps if you have an idea what you want when you go in, as it seems to focus them and they won't try to upsell you a bunch of crap you don't want/need.

Oh yeah, I think you may want to look at network coverage maps to be sure whatever provider you choose has a good strong signal where you live and work. 

You'll also want to confirm that your phone is unlocked.