Gwynge,
Yes, it would appear to be disability discrimination within the meaning of a disability under the DDA.
However, the first problem you would have is that, if you took action against the UK CAA in the UK Courts they would try to apply the safety argument, although you could present evidence of FACT that, as the regulators of UK airspace they permit foreign pilots to fly commercially within that airspace whilst denying UK citizens the right to do exactly the same thing. They may have a problem claiming consistency across that argument.
The additional impending problem is that, as of April all previous requirements become EU law and the UK can simply claim that they are applying that law to the letter; subsequently any claim is against EASA (the author of the legislation) and not the CAA.
You can guarantee a protracted legal battle which would cost bonkers amounts of money.
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