I paid something of the order of £1400 for my Windcheetah and that was in 2003. When I sold it in 2012 or thereabouts, I was a bit bummed out that I only got about £1000 for it, but there weren't many buyers. The ones on eBay have been listed for months and months. The thing is that for whatever reason, second-hand bikes – and recumbents especially – are massively overpriced in the UK compared with the USA. For less than a thousand bucks you can pick up a late 1990s/early 2000s Lightning P-38, or a recent RANS XStream with trick wheels. Those were $3000 bikes when new.
An educated guess would suggest Nutty's Speedy is in the 290-317 serial number range. 17" front wheels but with the mk2 joystick. What is the availability of tyres these days? I had Moulton and Bridgestones originally, then used a succession of Stelvios; last time I looked the Kojak was the main tyre available. I've seen a few converted to 20" rims, which has the arguable advantage of making the steering slightly less enthusiastic.
The most useful dimension to those knowledgable about the Windcheetah is the distance from the steering UJ to the crank spindle, since that helps defines the absolute minimum inside leg length, but the recumbent world of sizing is largely arranged by ex-seam, that is, from the soles of one's feet to the back of one's bottom, as though sitting against a board propped against a wall with a pedal at full stretch. The seat allows quite a bit of hotching oneself backwards and forwards to find the right distance to the pedals before you think about sliding the seat fore or aft, though the bucket shape does have a sweet spot.