another vote for powerline kit.
We have a long barn, 15m short length of L-shape, 25m long length. 400mm thick walls meant the signal from the office in the corner of the short length wouldnt penetrate into the long length. Brand new radial wiring.
Tried a Netgear repeater which was a bit woeful (after trying an abysmal d-link one).
Powerline just works, although I found DHCP/IP management a bit weird for some devices initially but seems to have calmed down – more by fluke than anything Ive done to it…
I have one device by the router, another in the corner bedroom to supply the Vodafone sure signal box which can transmit/receive down both lengths of the house from the corner and finally another wifi repeater device at the other end of the house.
I get seamless roaming across the two wireless signals when wandering around with my tablet.
Might be upgrading to a higher speed version sometime to be able to add a Windows Media Centre extender to push TV/video to a room without an aerial. The slower hardware is perfectly fast enough for internet etc, but I gather it’s not quite up to serving fatter HD files.