I suggest you get a second legal opinion as that doesnt seem correct.
The British legal system is called "reasonable".
ie; "reasonable" grounds for rejection, beyond "reasonable" doubt, etc, etc. And if its not already gone through the courts, then going through them sets whats called a "prescedence".
It seems that the police height issue may have already set that prescedence - so if you want this career - and believe me, its the best career ever, get this sorted.
This is by far a very unreasonable basis for cancelling your employment.
And just a thought... [quick laugh to end on]
You'd probably be going to Swannick, and, correct me if I'm wrong, but Swannick's ceilings are about 50ft up in the air.
Its not like your going to be a pilot in a finite about of space.
Anyhoo. Enjoy the weekend as best you can.
Any help I can offer, please PM me.
[I'm sure that goes for lots of us on PPRuNe.]
Bri