Are you looking for a modified example Dan? A thing to remember when it comes to S1's is that the value tends to increase on non-modified versions. Cars that are basically standard are going to be worth more in the long run than modified versions.
As the numbers fall on these a lot of car collectors are going to be paying big bucks for the unmolested examples - Mikey turned down 10K for his 20K miler mint totally standard S1 a few days ago!!
I do appreciate that the restored ones that are full of chrome and mods etc may pull the money at the moment, but as time goes on, and the numbers get smaller and smaller the value is going to be in factory standard.
Depends on what your initial investment is going to be, and what you intend to do with the car in the long run.
Happy days if you're serious about buying one of these beauties though!