Not a Caterham, they are a bit too pricey for me. It's based on one of the 20+ Lotus Seven style kits that are about at the moment. Mine is fitted with a tuned 175bhp Mondeo engine, Sierra gearbox and XR4 diff and brakes. You buy a space frame chassis and g/fibre body panels, fit Sierra hubs and diff and any rear wheel drive engine/gearbox you like. Using performance motorbike engines is very popular (plenty of light weight power, 0-60 in less than 5 secs!) at the moment. Car engines can be anything from 1300 Ford Crossflow to small block V8s.
Great project took about 500 hours. Budget is from about £4K upwards to about £8K depending on engines/interior and how many new parts you use. You end up with a very impratical car which goes like nothing else you can imagine! Everything else on the road seems like it is going so slow, nearer a track car than road plodder!
There is a big show at Donnington this weekend which if you are even remotely interested in this sort of thing is worth going to.
Mine is from a company called MK.
Best forum for a good read and 1st class advice/pics is called locostbuilders.co.uk. It started of for people builing very cheap sports cars but evolved and some very nice cars on there with big budgets.
Email me if anyone wants more pic/info.
Thanks for interest.