I've seen this in the flesh and it does look a little bizarre but very very light. apparently it is one of two that were designed for racing, but I don't know what kind of series, it would be quite insane on a track day.
Alan at SAR Countryside Classics in Kimpton has it in his workshop (that's where the photos were taken) its been there a while as I saw it when he was working on my sills. He had my car for 6 months and I went down a few times to see how the work was progressing. A word of caution though, if you are thinking about buying this, he stopped returning my phone calls after two months and eventually didn't finish the work on my car, he returned it not running and with bits missing (aftermarket JL Audio speakers, door bins, undersill trims etc) so I would be very careful that you actually get everything that you need from the Turbo S he is including in this sale.