They don't command massive money I'm afraid. I wouldn't think of it as an investment as there is no real demand or desire for these cars.
Schumachers are worth about the same as top end Abarth or maybe just a bit more.
Abarths are currently about £1,000 to £1,500. Schumachers are about £1,500 maybe a bit more for real mint examples from dealers with warranty.