I was never going to be able to justify to myself the £280+ that a working one from eBay would sell for. I had looked for almost a decade for a value for money one and it just wasn't happening.
The vendor was a very nice guy. Gave me loads of information up front which gave me the confidence that from the two I would be able to make at least one working one.
First job is to fit an IDE-CF adapter and then replace the noisy fans. Unfortunately Atari never designed them to be replaceable. The power & gnd is soldered directly to the motherboard. I'm going to have to desolder the old one and fit a header. If anyone is interested I'll update as I go.