HMV are selling the Friday the 13th, parts 2-8, in-store, for £3.00 each. They're the ones with the white covers. I picked up Part 7 - New Blood, and the picture quality is pretty good. There are no extras to speak of unfortunately, but they're still cheaper than online.
EDIT: I stand corrected - it's parts 2-8, not 9 or 1.