Looking for new mobile

My mobile phone contract recently ended and I'm looking for a new one.  Does anyone have any particular recommendations for something around £20/month with a decent amount of data for web usage and good rates on calls to the US?  I'm looking at the Samsung Galaxy S II on Tesco Mobile - has anyone used them before?  They offer a good amount of minutes and you can make international calls with Tesco's calling cards - the access number is free if you have Tesco Mobile.

I've also looked into O2's international tariffs - I'm tempted by that as they have a good amount of international minutes included (no need for a phone card, although they have those cheap, too) and they can provide you with a US number for US-based folks to call you.  That sounds great so my family could call me.

Anyway, just wondering if anyone has any experience with either of these networks or if you have any other recommendations.  There are so many options out there it's starting to get a bit overwhelming!

When researching for my impending move back to the UK I came across this website:

http://www.uswitch.com where you can compare tariffs for a variety of utilities, including mobile phone contracts and sim cards.

And, if you haven't already come across it, the Martin Lewis website, and weekly email, provide very good information on the latest deals: www.moneysavingexpert.com.

I'm in the States, have a Samsung Galaxy S II and like it.  It's my first smartphone, and does everything I want it to do.   

I just signed up for this SIM-Only deal through Orange, with £80 Quidco cashback.

It's a 12 month contract--with 300 minutes, Unlimited Texts, 500MB Data, and (after taking cashback into consideration) works out to be less than £4/month!

I personally prefer to buy an unlocked phone and get a SIM-Only plan, as I think it works out to be a better value.  My phone is relatively "old" - I got it from Carphone Warehouse in the spring, a Google/Samsung Nexus S, but it's always one of the first to get the new operating systems, and I love it.

Good luck with your decision

I've also just been told to point you in the direction of the Nexus 4 which is "Magggnitudes better than the S2" (in the boy's opinion)

As far as I know, T-Mobile offers unlimited data on their smartphones which may be important to some. I like never having to worry if I am crossing a limit.

I found http://www.billmonitor.com/ really useful when I was choosing my new phone, you put in your needs and it helps you find the best phone/deal for you.

I'm on T-Mobile, and they've been offering unlimited data in the US for at least 2 months now.  I don't have it, opting for the Preferred Android with a 5GB soft cap.  I'm often in places where I can jump onto free wi-fi, so it's not an issue for me.