At the price Fraser is offering it, it's a relatively good purchase. However, for what the original retail price is, this is junk, even if you consider that it's a high quality, custom sensor, NEC Avio camera stuffed into an Agilent gun-style housing.
For £4000 you can easily get a FLIR E53 or E75, ex-demo or otherwise, and hack it to 640x480 native resolution(though it's Linux, might require investigation).