In my opinion and seemingly that of my psychiatrist's, going down from 400mg to 300mg straight away is not a slow reduction at all. If I did that I'd never have been able to cope! When I was on 700mg, I went down in 25mg each week. Some weeks were 50mg. I feel that's a much easier way to go about it, with the least noticeable effects, even though it takes a while down to 0mg (hence the occasional 50mg decreases in dose).

As suggested by 888, Melatonin is a good option and I've found that Melatonin Extended/Slow/Prolonged release tablets are best for keeping me asleep. Circadin is an option for the prolonged release.

Other things to try include avoiding all sources of emitted artificial light, such as tablets, phones, lights, lamps, computing screens and any other device containing a light emitting diode (LED) for at least half an hour before you intend to fall asleep. Reading is good, a kindle (original) is fine as it does not emit light. Also avoid stress and movies, TV etc for at least an hour before.

Avoid caffeine for three hours before sleep, as well as excessive sugar. Don't eat less than three hours before sleep. Get into bed and lie in darkness or low light for half an hour before the time you intend to sleep. Reduce noise levels to a bare minimum.

Most of all, don't stress about not being able to sleep. Worrying about it exacerbates the situation. Also, ensure you stick to a sleeping pattern. If you're waking up at 9am, try sleeping for 10pm, 11pm at the latest. 8am 9pm or 10pm latest and so on. If you're waking up late you won't sleep until late.

Sorry about my disjointed writing. Battery is about to run out.

Hope this helps and good luck