Normally road cars sell around £12-16K. The race versions are usually cheaper, although they are less common.
This one is road reg'd so handy, but not as nicely built as a proper road car, with the trick doors etc.
A lot depends on how much spare stuff comes with it, rims bodywork etc.
I'd have thought £11-12 is fair enough, but it all depends on whether there is someone out there looking for one, race cars almost never come up for sale, this is only the third race car I have seen for sale in three years!
As an owner of one I would say that £16K is a very fair price!!