Is there someone out there, perhaps a genius in “price indexing” , who might be able to help me with this pricing exercise:

If the cost of concreting and then pebble dashing an exterior rear wall on a second floor flat in 2008 costs £2,667.02 (which includes 17.5% VAT) what would have been the likely cost in 1999?

I do so hope that someone will help me and also tell me how the calculation was done.

Duncan Bain, Falkirk, Scotland