Both are two-disc sets of the UK version of Queer as Folk. This is the cheapest I could find these, with play.com coming a very close second at £5.99 delivered for series 2 and £6.89 for series 1. The next closest I could find was £12.99 at HMV for series 2 and £9.99 for series 1.
This is perfect, if, like me, you only need one of the series (I already had Series 1 and just wanted Series 2). A few weeks ago HMV did have both 1 & 2 in a set for £10.99 (as Matt10 posted), but I passed as I only needed the second series.
FYI, HMV has put the Queer As Folk: Definitive Collectors Edition back up to £27.99, but Amazon has it at £13.97 if anyone wants the collectors' edition.