Whenever I have spoken to Birmingham (and it's quite often because I go round the west side of their zone when going south), they have always been very helpful and polite. I have asked for a zone transit in the past and got it, but it was a couple of years ago now. Whenever I have asked recently I have been refused (no doubt for good reasons), so I now don't bother asking and plan to go round, which I think lowers the stress for everyone! My opinion of Birmingham ATC is that they are helpful but busy - certainly not impolite.