Can't say I can ever recall a case where the middle/next has been blocked around me as SILV or GOLD which wasn't just pure luck (e.g. an otherwise 100% full LHR-ARN on a 767 as a SILV in Y - definitely not the only Silver nor highest card holder in Y - and the one empty seat on the plane seemed to be next to me at something like 7A as far as I could see). On UK Doms, my experience is I MMB/OLCI to 1/2C or similar and then some bloody couple gets in to the AB seats almost without fail Such is the attraction of being near the front, I guess, people would rather take 1AB with 1C occupied than 12AB with 12C free (for example).

Phil