Melantonin is prescription only in the UK. I’ve got a giant bottle I got in a chemist in Singapore that I hoard.
Be careful though @dktrfaustus - one of the side effects is really really bizarre dreams. I think it’s not so noticeable when people take them for jetlag to reset because your brain is fried then anyway, but when I tried taking a few to sleep better, the difference in dreams was very noticeable.
Valerian is a gentler herbal alternative. Makes cats love you too.