Have a nosey in the MB Club Gazette - both for cars for sale and a possible inspection. Chris Bass, authour of that book, may also be prepared to look over a car - but more likely if you stump up the £35 for membership there (worth it just for Gazette alone in my opinion). Also have a look on classiccarsforsale.co.uk
If the car is in S London, have a chat with Michael Lavers at Silver Arrows in Putney. He may be prepared to have a look over a car. A lot will depend on it's location, however. A few specialist dealers (Ironside/Crawley) may also be prepared to travel to look at a car but if they are busy may be less inclined. If it's close, as suggested above, someone here may be prepared to look it over. I'd hate to volunteer anyone though, although one name springs to mind.
Good luck. I had my very filthy 280 out in S London this morning and it was great - missing petrol filler cap aside