Depends what you plan to use the connection for.. You could either go for 2*85mb homeplugs for around £50, or 2*200mb for around £120.. I've got the devolo 200mb ones and they are fine - however it will cost me a lot to add another machine on to the network - not so if I had the 85mb version.
If all you need is streaming stuff and the occasional file transfer I'd probably go for the 85mb version.
Search for eConnect homeplug, they are about £22 each, much cheaper if you buy 4 or 5, ive been installing them for loads of my customers and they are some of the best 85meg homeplugs ive used, im amazed more people dont stock em, failing that MSI do a good twin pack for under £50 which is great. you dont need to spend 80 on 2 plugs, in fact you might get 2 x eConnect 200mb ones for that but ive not used them so its your call