So, this will work for some people - seems to work for a lot - and can seriously speed up Friends activity feeds, Achievements, anything server side based.
Go to
https://code.google.com/p/namebench/downloads/list
Run namebench without doing anything else, takes about 5 mins. Itll test DNS for you and recommend any local to you which perform better than your auto-set ISP ones.
If you find a better one, then go to
Home -> Settings -> Network -> Advanced Settings -> DNS Settings -> Manual
and set to what is recommended.
Big difference for me on talktalk, and two mates on BT.