You get £4.89pm discount on O2 broadband for having an O2 mobile.
All ISPs bar none have an FUP. That includes O2 and Be.
The O2 one has never been enforced so far as we know, and there are apparently users downloading more than you expect to.
With Be we know of one case where a user got an email (and he later says it was a polite email) asking him to lay off a bit after he downloaded 500GB in a month.
But! It turned out later this was at a time when there was a known cable break showing on the support page already screwing everybody, so he wasn't exactly helping - so fell foul of affecting other users.
He also said later when this was brought up to answer a question like yours here, that he had since downloaded over 500GB in a month several times since without a peep from Be.
I don't do gaming. Is XBox stuff interactive against other players and so pings/latency matter?
If so then Be would be better for you as on Unlimited and Pro you can have interleaving turned off to improve pings. On O2 you can't - interleaving is on. On all other counts O2 is the one to go for.
Have a look at MKD's
excellent comparison of O2 and Be, specially the separate up-to-date Page 4 with the costings over the first year, and details of cashback from various places.
Make sure the place is close enough to the exchange to get decent speeds.
Edited by RobertoS (Sun 06-Sep-09 23:26:37)