Your accountant is quite correct, however you have to be able to prove that the flying costs are towards a professional career. Hence post PPL ground exams and training for the GFT/IR and any professional ratings, medicals and admin costs could be tax allowable. Hours building post professional exams or GFT could also count if properly recorded, however the tax office would have a strong case for argueing that pre GFT or professional exams flying, if paid for by your company, was in fact a benifit in kind and hence a tax burden on you.Away days to LFT etc are always questionable.
If you joined a syndicate for flying, the detailed breakdown of your membership costs, showing, fuel, insurance and repairs would make for a good tax allowable case.
If your claims are reasonable, and you show some flying as pleasure with no costs being claimed, then you should be ok. Should you seek to overclaim they now have aviation experts in house..
In short, you have to be in a position to start professional training, i.e PPL passed, and be reasonable.
Good Luck.
(ex tax man)