not quite true, be/o2 are uncapped and unlike vm (who i've just left) there is no stm limits. the limits and times of these (for which there is a lot debate about if you google) are restrictive. the current limits are restrictive enough but the new trial limits (which will in no doubt be brought in) are worse. but worse than that is that they cap your speed by 75% (if your on 20meg to 5 meg) if you go over the cap limit. now currently it's 3gig (up and down combined) which you can hit quite easily.
you say that your going onto the 50meg tier, well good luck with it. if it's anything like when we had the 20meg roll out then there will be problems, and i can't see the stm (which i don't see there not being one) being any less restrictive. and as for gaming, in my experience vm are average. their routing is pants. for instance take cod4 - the route between me and my clans uk server was 12-13 hops and always got (since the 20meg roll out) big packet loss of 30-50% now i've been with o2 for a week now and the same server has 6 hops and hardly any packet loss. now i know things will be different for others, but i've spent the last year complaining about it but nothing has been done - but they are still happy to take the money and run. just wait until you need to speak to tech support eastern division when they know nothing about 50meg.