So today I dug out the old invoice for when I moved my PC to 8GB - £32. And found exactly the same components on the same site (Crucial) - and it's now £54.
Is there a supply-chain issue that's caused a near doubling since last August?
(It's this piece: http://www.crucial.com/uk/store/partspecs.aspx?IMODULE=CT2KIT51264BF1339 )
Original post on Dreamwidth - there are comments there.