1965-
I was extremely lucky and happened to see a week available online about 60 days prior to check-in. I believe there were about 4 developer weeks deposited, a mini bulk bank. Since then I've only seen 2 weeks, just prior to Christmas at the last minute. I don't expect to ever get another exchange into the London Marriott.
Very few weeks get deposited with II, the owners use them or trade within a different exchange program. I don't recall the specifics, but you could exchange your unit to Ritz Carlton residences and other high end properties.
Anyway, I know many Tuggers have tried and not been successful with an exchange to this property. No matter what you have to offer II, if they don't get weeks deposited you won't get an exchange.
Sorry to disappoint you, but it's almost impossible to get a week there!!