I have purchased a new hub from sky in the hope that it will improve internet coverage through the house, I still have the original one that came when I first took broadband with sky, is it possible to run both at the same time ? maybe one upstairs and one down?
Nope - you can only connect one hub/router to your phone line at once.
It might be possible to run a lan cable from the new hub to the old one & use the old one as a separate wifi access point - but you'd need some decent techie advice on how to do that.