Picky,
I believe MSF QXC flights are done from airfields away from Manchester; for example Sleap, Tatenhill etc. There would be a dual leg eg. Manchester - Sleap first.
As for the curfew, I could be mistaken but I thought it only applied to departures with arrivals being allowed later on without financial penalty. I stand to be corrected on that though.
In my admittedly limited experience the controllers at Manchester do their best to fit light aircraft in expeditiously, and holding for more than 5 or 10 minutes seems uncommon at the moment- in fact I've been cleared Stretton, Rostherne, Finals 06L on more than one occassion in the past month! Of course it all depends on the time you choose to fly, and I'm not making out that this is always the case at Manchester.
Cheers,
Eurotraveller