Surprised that it worked in Edinburgh, having tried to use it a few weeks ago at Sydney over the new year was disappointed to find only a hugely expensive room rate available (600AUD, min stay of 3 nights).
However, good for you - I use it regularly and its a big positive of Marriott for me, compared to the Hilton where the diamond override is hugely overpriced ( prices in atrack rate, so, typically 3x the normal price of a room). Plus Marriott's IT is second to none for website/channel integration etc, great you can easily use it online etc.
Enjoy your stays!
PS: Brum Marriott is very nice too!