Saab
I did not know that there is a Maplin's in Soho!
I use Homeplug on so-called 85 Mbps. I get about 16, but that's from a scrappy Samba NAS. If you are going into Homeplug please note that the 14 and 85 variants are incompatible with the 200 technology (although not mutually exclusive). 70 GBP gets you 85, 130 for the 200. It's less than I paid.
Worth every penny - It. Just. Works.
You might be able to offset the expense by on-selling the technology to your parents, or better yet, charging for their bandwidth
BOFH