Thanks for the replies, I really appreciate the detailed responses. I'll think I'll have to do a lot more research before deciding on building anything from the ground-up, but given the budget and the fact I'll need to get up to speed on how the machine works anyway, that's no bad thing.

One question on the closed loop system, is that something that can basically be added to any mill or are custom controllers / sensors required?

And for Jazzcnc, I've read a few comparisons (and still don't have an answer!), but is the watercooled spindle significantly better than the air cooled to warrant the additional complexity of a plumbed system?

The last CNC machine I had experience of was a Datron M8, and I see they do have an 'inline' mini-mill which looks great, but presumably as a 'POA' product, this isn't one for a hobbyist?!