Time for an update, helps me keep going.
Progess is slow; hit a problem; lots of things half done, nothing finished.
But it's OK! Progress is good and I've had a major success.
The problem is that I do need to drop the diff (as advised), but it's going OK. The handbrake cables are disconnected (easy via access holes), all the nuts are free and the long bolts are not seized. I have made a cradle, and a platform lift has arrived today so the job may be much easier than last time.
With the good weather, I've been working on the paintwork. Loose areas have been chiselled out back to solid attached paintwork, sanded to feather the edge and give a good key. There were two small cracks in the paint, I made a shallow V and filled with epoxy filler. All these places have had a few coats of paint and are getting close to becoming level with the existing paint.
The objective is twofold. To get a result that looks OK in photos, to get a reasonable agreed value before I (possibly) drive it to a dealer for the engine work. And to prepare it well for a respray.
Well in fact the results are very encouraging. Where the existing paint was sanded down, the match to the new paint is very good. Not 100% right, but close enough for me. So I had a go at a panel, upper rear quarter, sanded it wet with 2500 grade, then finishing compound and results are good!
With a bit more of the same and 2 grades of compound I think I can do better, to get close to the quality of a respray. So I'm carrying on and now taking even more care.
In the picture you may detect that the upper right region looks a bit better than the rest; in real life it is more apparent.
The roof is not good so will need good preparation and a repaint; I plan to do this by brush. Don't pull funny faces, I've done my boat by brush and people thought it was a spray job. To do a good brush job needs good preparation with very fine sandpaper, the paint needs thinning right down, use a top quality wide brush (costs about £15), spray the paint in the kettle with thinners now and then, work quickly, and change the brush after a few square yards (should not be necessary for the Lotus roof).
The plan for the next week or two is to drop the diff and do most of the work (one adjuster needed, will take a while to get it, covid at Lotusbits); and get the roof prepared ready for its topcoat.