I do like this sort of thing as defending those that do it it helps keep my own a/c in the air!
Claiming tax relief on training costs is quite clear cut really, but because the IR do not apply it evenly across the board, those that get away with it form the basis of folklore suggesting just about anything goes. Without getting anoraky about this, you as an individual can only claim any kind of tax relief on training costs that are wholly exclusivley and necessarily incurred in the performance of your duties. That is to say essential for each and every holder of your type of job to undertake in the performance of their job, not just something you fancy, or might be useful for the future, and most definitley not something that merely puts you in a position to do the job. For example, the cost of an IR is not a cost in the performance of a F/O duty as it is a prerequisite of being a f/o; the revalidation however may be a different story if he had to pay it himself.
Forming a limited co to funnel all these expenses through does not change the basic rules, but brings up the question of relief against what? IF the coy has no income there is no tax relief to have. If you channel your otherwise salary through the co, you open up a whole new can of worms in the shape of benefits in kind, and even the dreaded IR35 charge - it is not exclusive to IT consultants.
If you have another business and fund your flying cost through it there may well be scope to reclaim the VAT, and even get a measure of relief on the genuine business trips, but any training would almost certainly be a benefit in kind taxable on you, although you would get a corporation tax deduction on the costs, but this could be at half the rate of the BIK tax. There is also the extra cost of class 1A National Insurance to pay.
If you do go down this route, expect a fight, don't expect to win, and read up on interest and penelaties. However, if your accountant says it's OK, check his professional indemnity cover, do it anyway and sue the ba**sta**d when you get the tax bill!