There was an artical in Car and car converstions a couple of years ago with the Greame Wright Gould in. That said then the engine was around £20K, the chassis about £40K and then the gearbox (F1) was quite a bit as well. Total around £75K minimum to buy new.
Not sure about the Pilbeam, but same sort of money. Running costs, you need an engine rebuild a year minimum, same with gearbox, new tyres every meeting if not more, add in any accident damage and accomondation, etc, etc
CCC has also done a review on a couple of bike engined cars , and they are talking about £30-40K to be on the hill for.
Hope that helps