Cheers.
I already have a booster plugged in upstairs but signal still isn't brilliant. I did think about running a cable back upstairs but thought it would be look untidy from the outside plus wasn't sure on price of a 6m cable (for example) as opposed to a connector and 2m cable if I spliced in next to the bedroom window.

I think I may go for the Y connector (which I also have already: I live in two places with work and have doubles and extras of loads of stuff, tv, video, stereo, PS2's, stereo and tv cabling ) then run a cable upstairs.

Thanx for your advice.