I, too, have the change in bank account details email, and it seems genuine.
Interestingly, continuing from Paul's post, I sometimes use the 'marketplace' feature on CurrencyFair, and, for the life of me, I can't figure out why the trades from below the 'current best price' haven't been 'matched' - but there they are, stretching down the page from the 'current best price' for many cents below the current price - i.e. it really MUST be all smoke and mirrors - well, more smoke in this case.
I actually tried to put a trade in for a price well over the current market price, for eg. about 6 cents above the current price, and I didn't see this bid appear in the 'market' page at any point - I left it there for several days with no sign of it appearing. More smoke.
Today, I made an exchange, and tinkered about with the market, putting in high bids, then lower bids while watching my bids and other peoples around mine - there was a little jockeying while I 'played' with 2 other people who were putting in bids around the same price - both of us lowering our bid to be the closest to the 'next best' rate. There was no sign of the 'current best price' bid being matched, so I carried on watching for a while, and then tried an experiment - I put in a new bid at 0.01 cent below the 'current best price' and *bingo*, it was 'matched' straight away!
In short, Paul's linked article seems to be right - if there is an imbalance in 'peer to peer' exchanges, then the web-site itself must be doing the exchanges and then buying the currency it needs through normal FX channels. I'm not complaining, I still get better rates with CurrencyFair than ever before, and they must obviously need to make a smaller margin because they have fewer traders and other outgoings, and can afford to make better deals for the client.