Hello fellow gamers.
I have discovered that by having a higher than normal SNR (normal being the level that the DLM has chosen for you) you will receive a much better gaming connection.
In a BT exchange there is a machine called the DSLAM, this is where the line that runs from your house goes to and within the DSLAM is a system called DLM (Dynamic Line Management system)
These machines will automatically chose an SNR level that best suits your line so that you receive the fastest possible speed.
BUT, dont think that by having the fastest possible speed that you will gain the best possible gaming connection!!
By raising the SNR level 3 or even 6 db will slow down you speed half a MB or so but will seriously improve your gaming connection.
SNR means noise margin and you can check what yours is from your routers settings, look here if your need help http://www.kitz.co.uk/adsl/frogstats.php .
... And another thing dont be fooled by the fibre optic commericals, you dont need those super fast speeds for gaming. 2MB is plenty, just as long as your not doing anything else on the net at the same time.
I hope this helps you gamers out there. I know how frustrating it can be!
Peace.
P.S. theres just 1 problem actually getting Virgin, BT or who ever to change the snr settings for you can be quite difficult.
GOOD LUCK!
1 of the Virgin mods on their forum told me they could "Lock" my snr and that i needed to phone up to raise a "trouble call ticket". So i phoned up and they put me on hold while they spoke to BT but BT said they weren't willing to send anyone out to the exchange. 
