I seem to have discovered something that reduces my insomnia; no guarantee that it is a universal treatment.
A couple of months ago I bought some Evening Primrose Oil to test whether it had an effect on my ME symptoms (no). Since I had it, I continued taking it, usually three caps twice a day. At some point, I realized that I was sleeping better: having fewer 'can't get back to sleep' periods. I still wake up several times each night to pee, but I can quickly fall back asleep. Then those insomnia periods returned. Very annoying! Then I realized that this started up again about 3 weeks after I ran out of the oil. Three days after buying some more, I stopped having those insomnia periods. I'm not sure of the statistical quality of this, but I'm certainly going to continue taking it. I'll try experimenting with lower dosages, to see how much is required.
Borage oil is also high in gamma-linoleic acid, so that's another possibility, although it sounds like is has more potential harmful side effects.
It's Jamieson brand 500 mg softgels, although I wouldn't be surprised if all the brands on the market came out of the same processing plant.
Sleep well.