On the subject of tax relief on Balpa subs, I have heard several different versions of "you can" vs "you can't".
Speaking personally, every year I put down on my tax return under job expenses the full cost (to me) and I get back on my BS 02/02 form (PAYE Coding Notice) the following:
Note 10 Professional Subscriptions £ 361
under "Your Tax Allowances.
Hope this is of use. Has anybody tried the same with Flight International and got away with it??