I presume the car is not LHD although you say it was imported. Do you mean when it was new?
£9500 is probably OK since the mileage is low. The problem is that low mileage is not always a good thing. Lots of things deteriorate when the car is sitting, like rubber seals. And gaskets like you are seeing.
I bought a low mileage 380SL and quite a lot of minor things needed renewing due to age.
There's a 1987 300SL 'show car' on ebay at £7k and no bids http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=2434042806&category=9855