Something definitely to consider over homeplugs or boosting the wireless. Although since my current Belkin only supports 'G', 'N' may well be enough of a desired improvement. I'm not au fait with Plusnet's router offering and whether it's any good. Chances are I'll buy something else in time anyway.
I'm in Herts, I've already spoken to a couple of well rated guys broadly about what I'm looking at. Initial prices quoted seem extremely reasonable. I'm following up with a few 'on-site' photos via email.