Thanks for the replies and advice guys!

I wasn't really sure the best way to machine this piece, I do actually have a lathe, but I wouldn't really know where to start with getting the piece center....

It looks like you've chosen 7208 bearings, which are bigger than you need for a 25mm ballscrew - I'd use 7207 instead to reduce the moment of inertia and cost. Have you drawn the rest of it?
Thanks for that advice Jonathan, I was just allowing a little more clearance for the screw, but I think the 7207 would be better like you say.