Dual Lenses should be cheap enough on ebay. I'd say get em if you can. Alternatively TK Maxx or Decathlon will be as cheap and you can try before you buy that way. Either way you'll have an awesome time so I wouldn't get too hung up on it!
Also, don't put them to near the fire to dry them out, I melted both my wifes and mine year before last...wasn't best pleased to say the least...didn't learn my lesson either, did the same thing with my gloves last year !!
Forget buying them here. I bought some singles before I went then half way through spent about £3 on some duals in Bansko from a cheap non brand shop. They are excellent - just the trick.
Buy dual in Bulgaria for a fraction of the price of single in the UK!