Cot sheets are a great thing to wrap in too. When we were in the Cook Islands last year, we put Jenna in a short sleeved onesie, and a nappy, and just wrapped her in a cot sheet with a cotton cell blanket over the top. It was 30degs and humid most nights (and we had coem from Melb winter) and she was fine. She was actually 4m old then
Besides - that was the only time I've really ever used my top cot sheet!!