Please excuse the ignorance, and apologies if this has been dealt with before.

As a novice who has yet to actually use Avios, but who would now like to use them up, it seems that flight taxes on flights (especially long haul) make the value of Avios pretty small. Am I right in thinking that there is no way of off-setting taxes/surcharges with more Avios?

And as a matter of interest, are the flight taxes a reflection of actual taxes levied or are they a charge determined by BA as part of Reward flight marketing as a function of the particular routes?