OK, I really should be in bed but this is bugging me.
I went through all the little bits I sort of know on this PC and checked my ip addresses (ipconfig /all) then checked that with my connnection properties and I was one digit out on my default gateway.
So I changed that and booted up Limewire again. The download kb/s shot up to 250kb/s and I almost leaped with joy. But by the time I'd logged on to here to say I thought I'd resolved it, it had dropped right back down to 0kb/s !!! Which makes me think it is something I've failed to configure here. Anythoughts would be aprreciated still because my technophobia is annoying me now (and stealing my sleep)