problem solved, rather sneakier than fuel rail pressure….
Replacement crank sensor, (pattern part…. I know…. don't bother lecturing me…. it was the quickest cheapest solution…. ) had a plastic spacer ring around it…behind the rubber seal ring… . In the half light last night, didn't spot that it hadn't gone all the way home, did the bolt up so tight it cracked the body around the brass insert, but couldn't see that it wasn't all the way in….. removed it today, having got the thing back up in the air to get under it…. and spotted the issue….
solution…. remove plastic ring, replace with the now rather hard and inflexible O ring seal from old sensor…. only marginally shorter, but will at least fit in the receiving hole …. then refit nice new flexible seal in front of it, then refit new sensor, and use a wider washer on the bolt to spread the pressure on the mount …..
cabling routed up to gearbox coolant ? pipe still in heat shield, and loosely tied, then up to brake lines, also loosely cable tied, then across the top having rotated the connector plug around to face back towards the passenger side…. plenty of slack, and completely clear of exhaust etc….
car now starts….
it's still breaked every other way from xmas… but it starts !!!