DIY Router Design questions ?

Hi all,

I'm looking at the feasibility of building a small low-cost 5-axis
CNC wood router for the batch production of decorative knife handles,
etc. and would appreciate any advice on the pros and cons of the
different design approaches commonly used in CNC routers.
My first thoughts are to use bolt together aluminium extrusions with
linear slides, leadscrews and servos, but have a lot of questions.
In gantry style systems where the gantry is driven from both sides,
what's the best way of synchronising both the leadscrews in case the
gantry skews ?
Does a rack and pinion have any advantages over a leadscrew ?
Is it worth looking at linear motors ?
Given that each part would need use of a roughing and a finishing
(fine detail) tool, I'm looking at ways of mounting two router heads
to save tool-changing, has anyone tried this ?
Does anyone in the UK know of suppliers of low-cost aluminium
extrusions, linear slides, etc?
Any other thoughts on what I've overlooked ?

Rab,
Rainnea Graphics
http://www.project.rainnea.com