Found a good deal with Cornerstone offering 1,000 Avios for signing up to their cancel-any-time razor blade subscription service. The cheapest plan is £20, and if you attempt to leave the site, they will instantly offer a £10 discount on your first order, essentially bringing it to a very nice 100 Avios per £ - not to mention (supposably) high-quality razors and a monogrammed handle delivered to your door for a tenner?