If you could drive it on Sundays and enjoy it, go for it! If you want it to be an investment - what is it? I know pommy sports cars.
Generally speaking cars that will be collectable reach the low point of their value after 30 years. the trick is to identify those which will become desirable. Gull wings aren't a guarantee - yes, the Merc, no, the DeLorean. The DeLorean will always have a quirk value because of the movie, and because of the stainless body - but the chassis can rot 'cos it's steel. But I doubt that's the pommy sports car you're talking about.
C'mon, what is it? I promise I won't bid - I got a 1985 RX7 Mk III a couple of years ago, I reckon that's the classic shape and will do well (already offered 3x what I paid for it, so I could be OK there) and it will be fun to drive.
