It's worth what someone is willing to pay when you're selling it.
If it were mine I would start at £20K and see who's interested.
Realistically I would expect to price it around a comparable model by year so "average" Escort Cosworth money or top racing puma money?
It's a recognised firm that built it which really helps IMHO

The main issue is it's a toy, most people could end up spending that on a toy but in nibbles and mini bites not a chunk!
is it eligible for any motor sport race/rally I'd check that out to widen the audience?

Same old forum story here, I'd love it but atm I would have to sell one of my favorite cars to fund it which won't happen