I am aware Tiscali in some European countries are applying filters to slow down p2p share programs. I don't know if this applies in UK. Once they detect someone using large amounts of bandwidth, they apply the filters. They would be unlikely to admit to it though.
If things have all of a sudden gone awry then you could try deleting your LW Preferences folder whilst LW is closed; instructions here:
Fixes for Limewire If that doesn't fix it then ... it could be your isp provider if it continues to persist to be a problem.
Try the magnet links Stief was refering to in his link. If you get slow speeds with those files then you know there's definitely a problem!
(
ISP's known to BLOCK or Filter p2p or specifically Limewire)