I have a Hobbymat BFE65, mounted in the KT65 co-ordinate table (although this is technically an option, in my view it is essential - it turns the machine into a proper milling machine). It is a very sturdy machine, heavy for its size which helps with working. While it looks as if it is a round-column mill with all the problems of loss of position when changing the head height, in fact there is a key-way on the reverse of the column, and the head is aligned with this key-way with adjustable gib strips, and this works well. It is the most rugged small mill I have seen if you are pushed for space.
As for value second-hand, I don't have a real feel for it. They are very rarely available anywhere (at least when I was looking for mine
. I have seen a couple on ebay(BFE65 head only) which went for around £300, but that may have come down with a wider range of mills available these days. I've only ever seen one other than mine as a complete machine, and that was in one of the second-hand machinery dealers, at around £650 with some tooling.
I am about to take delivery of a Warco WM-18 as my next upgrade, so the Hobbymat will be for sale then. If you are looking to buy/interested get in touch and we'll see if we can work out a satisfactory deal for both of us.