I can't offer any practical help, being a mere 6'2", but I'm absolutely disgusted that you can be excluded for such a rediculous reason. If you're capable of holding a Class One medical certificate, that should be all that matters on the health front.
NATS had a wheelchair-bound trainee while I was a student ATCO and while it's absolutely right that he shouldn't be discriminated against, a tall person is much less of a H&S risk than a tall person.
My advice is get a good lawyer and fight like crazy for your rights.
All of I sudden, I'm very glad that as of yesterday I don't work for NATS!