Take GBP 100 of Levs and change anymore you need in the resort. Good rates here in the UK, especially at M&S or Travelex. Tbh, you won't get too much better in the resort.
i spent almost the whole of last week changing moey in hotel samakov foyer for 265 lev / £. then realised id been walking past the bank next to ski depot in hotel offering 279.75. i must have walked past 15 times before i seen it. doh!!!