I'd echo out esteemed leader's view - you wanted it when you bought it and it's probably better the Devil you know now. Certainly in comparison to selling it and buying another I'd probably advise sticking with it as there are virtually no perfect cars for sale and you might find you are looking at similar money to bring another up to standard by the time you have lost money selling yours and paid more for another that will almost certainly have its faults.
I'd say a good S2 coupe sells for approaching £6k and as Paul Mc said I'd counsel having a 4-figure sum available to address issues you uncover even on such a car, so you're quickly north of £7k which is not so far off your estimate, especially if you lost another bag of sand in the changeover.
I'd say a good S2 coupe sells for approaching £6k and as Paul Mc said I'd counsel having a 4-figure sum available to address issues you uncover even on such a car, so you're quickly north of £7k which is not so far off your estimate, especially if you lost another bag of sand in the changeover.