subculture, what do your accountants say in relation to using the tax you paid in the UK as a way of deducting from the HU amount? I've never heard of anyone doing it this way and I'm not sure if it's permissable. Perhaps, as you say, you could pay the correct amount due in Hungary and then claim back what you overpaid in the UK.
You'll find it much simpler next year if you pay tax locally in Hungary and then pay the remainder due (if any) in the UK. (By the way, if the income is from 2006, then you've already missed the deadline for payment in Hungary and may also be subject to a fine for late payment.)