Whilst looking around for a copy of the "Cosmos Rocks" 2LP vinyl set less pricey than the 23-25 quid it seems to be going for + shipping, I found this: http://www.amazon.fr/gp/product/B001DUKI3A
Amazon France has it for 16.23 EUR (13.57 EUR without tax if you're ordering from outside of France internationally).
With shipping for me, it came to 24.47 EUR (incl. shipping for Canada), which works out to be roughly $37.89 CAD / $36.10 USD (courtesy of XE.com) at the moment. It's about $7.32 CAD / $6.98 USD cheaper than Amazon UK atm.
Thought I'd mention that, for anyone still thinking about pre-ordering the vinyl set. Dunno if it's *the* cheapest it can be had for online atm (feel free to mention any other online retailer deals!), but this works out for me as I hate buying vinyl records with expensive price tags.