Few of us want to buy a new car and immediately set about fixing known faults. The response of us unskilled motorists is - if it really is an easy ten bob fix why aincha fixed it. (And if its a pricey fix we're probably not interested).
You might just need to be patient while a more practically-inclined buyer comes along.
Have you compared your pricing with similar P38s up for sale at the moment?
Is your ad sufficiently detailed - buyers won't travel very far unless your ad gives them a good idea of what to expect.
My 3 litre petrol BMW sold in 3 weeks and 3 days, to a guy an hour's drive away, so there are still buyers out there.