Oh heck, I gotta measure the CV flange distance!
With a bit of an unsafe faff, lifting each side in turn to get axle stands underneath, I managed to get the car up in the air on the stands, on loose and wobbly cobbles, and then gave it a good push and shake.
Satisfied it wasn't going to fall on me immediately I shoved it again and then got underneath.
The engine undertray then came off, three different types of screw fixings and a load of cable ties were holding it in place. I will revisit that when everything else is done and see if I can do a better job of it.
Anyway, with a light and a phone under the car, I found the CV joints and figured out how I could get a reasonably accurate measurement of the flange spacing.
I got some scraps of stick from the workshop bin and, with a couple of small G cramps, I made a simple caliper.
Back under the car I managed to get the caliper points to touch off on the rim of the CV flanges.
I was then able to Shuffle back out and put a tape measure across the caliper points.
248mm it seems, probably something like 245mm face to face ignoring the raised location rim.
I guess that is within the 5mm that is required