Thanks all.
Here are those interior and engine bay shots. A list of tidy-ups and some small-part replacements to take care of, such as speaker fader control wheel and new door mirror lenses. Car has new rear screen and weather seal. Dash needs some work because of the ubiquitous Australian sun-induced cracks. Leather and carpets all good.
I pulled apart, cleaned and fixed the Hirschman aerial and it now works. The Becker Mexico is period correct and even the tape deck doesn't sound too bad!
I pulled apart, cleaned and polished the Bosch fogs and repainted the cases with matt black. A fiddly job that won't be repeated often. Was very careful not to break the glass lenses ... the SL Shop in the UK charges more than GBP900 a pair, GBP400 for copies! Also pulled apart front grille and cleaned/polished.
Engine bay still needs detail. No timing chain rattle, RH cam shaft looks good under oil cap, subframe and chassis all look ok. Steering as direct as RCB will ever be, really funny after the C-class's electro-mechanical steering that points like a fighter jet.
Tyres are tolerable. Budget Nexens on the front, Maxxis rear. I hanker for some classic Cinturatos and dream of new XWX for the 6.9 (one day ...).
No corrosion problems.
I took car for 125 km run today with mix of windy roads and 110+ km/h motorway runs. Engine sings like a turbine at 3200+ rpm. Good pull in second up to a self-imposed limit of 4500 rpm/130 km/h. Car settles at expected temp of about 87C and 3 bar when underway. Photo was at idle in park on hoooooot day so temp had risen a bit. There were some slight vacuum leaks due to shrunken small blue hose pipes and loose plug-ins at their ends but with each one I address, the better the K-Jet gets in terms of smoother idle and no grumpy hot start any more (wish I could say the same for the 6.9 which needs attention to the AAV, I suspect, and vacuum integrity). After today's run, I checked consumption: 13.7 l/100km, always using BP Ultimate 98; very happy!
Cheers.