I take it you just took one of the empty rows?

Seat blocking has worked for me every single time. I haven't sat directly next to anyone on a bmi flight in literally hundreds of sectors - certainly not since the end of 2005.

I have noticed recently that the system has been altering seat availability for trim (yes, the loads have been that light!) which has produced some strange results. The other day I was offered only the middle seat in an exit row. I was expecting a horrid, crammed flight. Turns out there were fewer than 50 pax - I had the entire row to myself and there were people scattered about the cabin. Why it blocked the window and aisle in my row I shall never know.