All information comes from the Networks.
For that one you are asking about - http://shop.o2.co.uk/promo/iphoneindex
Scroll down to £45 per month and you can see it.
Remember, all information in my spreadsheet here - http://bit.ly/dqmdsn - is based on 3GS prices, but when the new tariffs are available, they will be put in. This is purely for a guide only to give you an idea what you can expect.
When Orange, Vodafone, T-Mobile, Virgin and 3 announce their prices, ill put it in there!
Ahh! I thought that pricing was for iPhone 4.