Congrats on the purchase Paddy,
But be VERY insistent on the paperwork to be delivered to you (including all initial Japanese importation papers and all shaken-s (Japanese MOT) paperwork. Have it veryfied by somebody who reads Japanese.
I had a small hobby project with Japanese imports (18 vehicles in total) and clocking is becoming a BIG problem in Japan especially with older European cars as more and more gaijins (foreigners) are getting in the trade. Besides these cars are only sold abroad so no responsibility here for clocking.
Basically Japan follows the German route it seems

. 20 years ago 'clocking' was virtually non-present in Germany but now it is really difficult to be sure about a used car mileage.
As for your car appearance - only two things would make me suspiscios about the claimed mileage - worn tires as you mentioned, the converted hood/trunk jobs and also the image of the engine - the underbonnet area looks like one of a 150 + car: air ducts are are way too worn out and cracked for a 70Kkm, there is lots of residue on pipes and the expansion tank is too yellow and opaque. The rad hose seems to be replaced recently though.
I am not saying the mileage is false, but be EXTREMELY attentive and careful.
Check the propshaft rubber coupling - it may be worn.
As advised already - start with ALL fluids replacement. Have an experienced technician to check the gearbox internals when swapping the gearbox filter.
Measure engine compression and replace all spark plugs.
Make sure A/C works.
Since you passed the MOT I guess there were no oil leaks (common trouble for Japanese imports).
And while the car is ramped - have a very close look at the body to make sure it was not repaired.
And for all readers jsut a consideration point:
At dealer's action last autumn a proven full history 1992 500E with 45 000 km (Grade 4.5) was sold for more than 30K USD.
Last summer - a 1992 500E with 4 000 km in NEW condition (Grade 5.0)- 75 000 USD!!!
Average condition (Grade 3.5) 1992 500E with 136 000 km - ~10 000 USD.
Average for a Japanese spec fully documented 500E is anywhere between 17 and 28-30 000 US Bucks depending on mileage and condition...
1992-95 400E/420E are aplenty and are very cheap (far cheaper than 6-cylinder and diesel models), as they are expensive to run and are heavy on fuel in Japanese traffic conditions but do not have any pedigree (my 92 400E with MB used car warranty and 45 Kkm cost 3500 USD).
500Es on the other hand are collectibles and are priced correspondingly.