Have you looked for LNF (look no further) rates by comparison shopping other websites? I have some nights booked at the Grosvenor House coming up in December and my rate is 98.00 GBP/night for the weekend nights. Sometimes you can stretch this to 4 nights so if your 10 nights include 2 weekends, you might be able to get a higher rated hotel for the same money. Likewise - you may be able to get Marble Arch for less. Also, peruse the "Deals" at the London hotels and see if any offer the "buy 2 nights, get one free". This has been a pretty steady promotion of late. If you have the time, I'd urge you to look into rates on other sites and then try to get Marriott to match. Read their Look No Further rate guarantee terms and conditions and give it a try