Thanks. Before I posted this, I had collected quotes from various places. Draminski (very basic design) about £350, Agritech, £325 + vat, PregTector £395 + VAT. Quite fancy the latter. Spec sounds better, and they offer an angled-top unit as well as a flat one, so could be easier when standing up.
Wasn't asking specifically for second-hand ones, but if someone has bought one and not used it much, I'd be interested. Probably going to bite the bullet in November and invest in one, so would appreciate any advice. Having one would save a lot of guess work and unnecessary/inefficient feeding.