Thanks for all the suggestions
I accidently came up with a solution. Was shopping for a repeater when I stumbled across a power line WAN system. It was cheaper than the repeater and I have a spare WLAN router so combining the two has been the easiest and most cost effective way of doing things.
Was impressed with powerline LAN system. It really is plug and play, with no faffing around or software needed. The one I got provides 85Mps data transfer, which isn't too bad and extending the system is simply a question of buying another adapter and plugging it into the wall. It all seems to be too good to be true, am I missing something fundamental here?