@Sister melatonin is a hormone that regulates sleep. I've tried taking it but it gave me a strange feeling of not quite being asleep which creeped me out. It's worth a try though as I know people who swear by it.
@kmakm if you surgeon doesn't like sleepers he shouldn't take them. That's got nothing to do with you, get your GP to prescribe you some. I worship my little bottle of sleep. I'm very careful about when I take them--three utterly shitful nights and the fourth is take a pill time. Knowing that I have them is very reassuring. Oxazepam is my choice as I can also use it as a sedative if I'm having something revolting done to my body.