Are you sure you'll need £600? How many of you are going? You'd be better off changing a smaller amount if you're changing it here, then changing at the bank in Pamporovo. The banks were giving around 2.90 to the pound when we went to Bansko in February. We only spent £515 between our family of 5 in the week. Admitted we weren't in night clubs every night but we were self catering and had 7 lovely restaurant meals with drinks and ate up the mountain every day for lunch.
We took some levs and changed sterling at the Alaska supermarket, got 2.76 at xmas. You will not need that amount unless you are planning to eat out every night, party till dawn, get taxis everywhere and there are about 5 of you.We brought £200 home (never before heard of) only spent £300 for 4 of us.