from what i can gather it really isnt that much more. i ordered mine today from tesco cus i couldnt be bothered with the hassle of getting it when i get there
if you go to the banks in the centre of bansko you'l get around 2.2 leva to the pound, watch out for the kiosks near the gondola, they advertise 2.15 then give you 1.9 because you'r not the 50th customer or some such rubbish !!
Just back,the best i found was 2.12 next to the Balli supermarket opposite the banderitsa hotel,
Great supermarket,only 1.99 levs for a 2 pint bottle of wonderful local beer
Get a Nationwide Flex account and use the cash machines, far better rates, exchanged £300 at 2.08 in Uk and while in Bansko got 2.208 or better with at cash machines.