Thanks so far for the replies - some good points raised.
The car does look in good condition - I haven't actually seen it yet, but all the photos are clear and look good. I was told they've replaced some of the tyres and also refurbished the alloy wheels - all normal for a car of this age.
The car has done around 33K since the last recorded service with MB in late 2019. The mileage is then approx 20/+6K, 21/+6K, 22/+9K, 23/+12K. There's the normal advisories such as worn tyres and for 205's, worn lower control arms on the fron suspension. However, what does concern me is the salesman, when I was haggling with him on price, did let slip they've had to replace the steering rack due to a leak - he said 'this is common on a 205' (1st I've ever heard of it!) and it seems odd for such a relatively young car. The option to verify the mileage on the car is to put it straight in to an MB dealer (of the same group) as it will have outstanding software recalls and when STAR is plugged in, it should alert if the mileage has been tampered with.
As tonysmb points out, missing history is of course why it isn't being sold though MB used-approved...and is cheaper. The other (identical spec) car I'm looking at is actually a 65 plate W205 with 69K and being sold via MB used approved by the same group and is the same price. So the options (so far) are one car with 60K/7years old and a 3month used-car warranty or the other car with 69K/7.5 years old with a year MB warranty. Both the same price.......