a car is only worth what some one is willing to pay, not the same as an agreed value with an iinsurance company.
basically, the fewer owners, the more history, the originality, no prevous damage, the more it is worth but ebay is a good guide for classics
start it at a £1 and let fate decide but a tidy a plate mk1 in black wont be worth less than a grand in my opion might be as much as 2 but with out seeing a car in the fllesh and knowing the provence just a guess
pictures speak a thousand words