Hi Lembrado
757 is reasonably busy year round at LGW with scheduled flights and quite a bit of charter night flying in the summer, but not as bad as A320 at MAN for overall hours. Unless the company obtains another 767 (rumours change almost daily) then you will have a long wait to get your hands on it. We are apparently getting rid of two 757's at the end of the year, which may mean forced draughts for lower seniority guys onto the A320 fleet if they don't get enough volunteers, however progression to the A330 is likely to be quicker than to the 767.
I'm sure you have read elsewhere that the interview is a fairly relaxed affair geared to see if you fit into what is still a fairly nice culture to work in.
Good luck.