None of the packages you have listed are truely unlimited. they all have a Fair Use Policy that limits your use.

Have you considered Vodafone?. I've not heard anything bad about them yet (they have a fair use policy as well)

http://online.vodafone.co.uk/dispatch/Portal/appmanager/vodafone/wrp?_nfpb=true&_pageLabel=template11&pageID=VA_0012

I have used Virgin and Tiscalli and would not recomend either of them.

Tiscalli are terrible, I'm sure you have seen the theards on this forum.

Virgin couldn't get me connected, they spent two months blaming BT. I got sick of their excuses and decided to cancel. They said I would have to pay £50 disconnection fee (when they were advertising a no minimum contract deal). I spent an hour on the phone to customer services. For some reason they could not understand that I was never connected and therefore a disconnection fee could not be charged.

I joined AOL next and was connected within a week (but i wouldn't reccomend AOL at the moment either)