Offer £400 cos...
It's a crap colour, rusty as hell, small engine, manual, no aircon, old smoker.
Then when you get it
Colour's actually ok, rusty as hell, 200 engine isn't too bad, manual DOES suit the engine, has a sunroof - who needs aircon, classic Mercedes.
If it's ok, they are a really really nice car to drive. I ran a similar one for a year, and paid out under £50 for parts (which it didn't need) - totally reliable.
If all goes well you can sell it when you've had enough of it, and not make a loss.
And if it all goes Pete Tong? You're in it for £400. Thats a months lease cost for a Fiat.
Edit: And the number plate looks like it
might be a private plate
(to untrained eyes!