Nice try, Imverge, but most merchants on that site don't deliver to the UK!
Bja200, Marriott Insiders has been offering 25--75 points off & on for liking, following, & tweeting certain terms, which post instantly.
Or you can buy 1000 (sorry, that's the minimum) MR points for US$12.50 (~= £9.10 if your payment card has a 3% forex fee HERE.