Aside from the M3, the E36 coupe is the most desirable and very good ones do seem to command prices north of £6k. For a saloon, you're looking at about £500 for a project car, £1000 for a scruffy runner, around £2000 for an excellent low-mileage example with plenty of history and in very good condition (expect to see a similar car on dealer's forecourt for about £3k). If you're still struggling to price yours, have a look around and try to find a similar example and price yours accordingly.