Michael,
Have you looked at Giff Gaff? They are owned by O2 and use the O2 network. They provide sim cards and you provide the phone.
Customer service is limited as it relies heavily on other Giff Gaff users providing support via a forum. I don't think you are tied to any contract with them (somewhat unclear from the web site). It is almost like Pay As You Go, but significantly cheaper. In fact it is cheaper than O2 in most cases. You can also set up a monthly direct debit for some of the items.
You can also get free Giff Gaff to Giff Gaff calls and texts. Pretty useful if you pay for two iPhones.
It might be worth your while taking a look at their web site.
The web site is not particularly clear & there are no stores to visit, so you need to relatively competent. It is who I am considering going to.
Regards,
Hval
