Also not directly related to London but did use a similar MR promo(1000 pts/night) for a stay in Toronto last month. After 10 days, the bonus points did not appear so went straight to Marriott CS because I knew from dealing with the front desk during our stay that they were well meaning but a bit clueless about their hotel promotions. The CS rep immediately gave the correct bonus points as "Goodwill Points" and made a point of saying that this was a common problem and next time if using this type of promo to bring it up both at check in and check out to have a better shot of the points being applied properly.