I haven't seen a sleep neurologist, but it might well make sense to see one privately.
As it is, I'm looking back over my life at different periods and what did or didn't work for me with sleep timings.
In the past, when my 'night owl' sleep became a problem, I'd stay up later and later until I was up until about seven, then get some morning sleep and up again in the afternoon, and an early night to re-set.
But I hadn't registered how episodes I've done of split sleep, where you get up in the night, actually helped to re-set. Bed later, later until say 3am sleep. Get up at 7, do three hours, go back to bed and sleep 10-2. After a couple of weeks, find I'm not wanting to do my second sleep and I'm getting to sleep at maybe 11-ish.
That being said, I've worked out my biggest problem at night is lying awake getting upset about stuff instead of going to sleep. Last night I identified what but didn't stop myself, however the night before, I did stop myself. Hope, then.
Right, I'm going 'helpful neighbour with smartphone' door-knocking. My GP wants me to email pictures of my chilblains/covid-finger. (I don't have a smartphone.)