Travel Technology - Best price on iPhone SIM cards with lots of data in UK

My iPhone 4 and I are going to arrive at LHR. Over 4 or 5 days, I plan to send back to the US lots of pictures and video. What company offers the most data for the least cash?

Many thanks!

Get a pay as u go sim card from Three, you'll get few hundreds mins and 1GB data if you top up £10..

Would definitely agree a Three sim is the way to go on this one.

Thank you for your quick responses!

Three (also known as 3 or Hutchison) have 7GB for £25 on Pay as you Go on their USB modem stick option (i.e. the non-contract option). three dot co dot uk is their website.

Other pay as you go networks offer less data as a maximum. And some do not allow you to top up another discounted pack within a month even if you exhausted the first pack.

Second choice would be T-Mobile.

PS Giffgaff (for calls) and Tesco would be worth looking into too - I gather Tesco has a cheap data deal.

Get a pay as u go sim card from Three, you'll get few hundreds mins and 1GB data if you top up £10..Their main PAYG page leads you to believe that the option has changed to 100m & 500MB of data for £10 now (or Unlimited data + 300m for £15)
http://store.three.co.uk/SIM_Only/Voice_Pay_As_You_Go

But if you drill a LOT deeper, you'll find the following:
http://support.three.co.uk/SRVS/CGI-BIN/WEBISAPI.DLL?Command=New,Kb=Mobile,Ts=Mobile,T=Art icle,varset_cat=payasyougo,varset_subcat=4124,Case =obj(4101)

That mentions that you can buy a 500MB add-on good for 30 days for £5.

But if you drill a LOT deeper, you'll find the following:
http://support.three.co.uk/SRVS/CGI-BIN/WEBISAPI.DLL?Command=New,Kb=Mobile,Ts=Mobile,T=Art icle,varset_cat=payasyougo,varset_subcat=4124,Case =obj(4101)

That mentions that you can buy a 500MB add-on good for 30 days for £5.
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