Wash my mouth out with soap, but try Dixons !
I had the same problem with my Sky Digibox, which is connected by coax to a TV in another room. Tried Sky Link - crap ! Looked at remote extenders and found them a bit pricey.
Wandered into Dixons on Monday. They are doing a 1/2 price sale ie £24.99 on a Matsui video sender that can be used as just a remote extender. Even comes with little "mice" attached so you can hide away the main units and point the remote at just the mouse.
Works great. All you have to do is plug in one box near the digibox and one near TV in the other room. No need to bother with any other leads unless you want the video sender functions.
Would not normally buy from Dixons or buy Matsui, but for the limited purpose I want its good value. Have not tried to use the video sender as TV gets signal through coax, but this may come in useful for TVs in other rooms.