Advice on small mill table conversion

I'm finding myself struggling to make headway on a number of my
projects at the moment and to help me out I'm knocking up a small
machine for milling/routing aluminium parts when required. It is
based on the Proxxon KT150 compound table, this has a table size of
8"X8" and a travel of 6"X6" which is big enough for most of the parts
I require. These include adapter plates, mirror mounts etc etc.

Here are the parts I have got together: the Proxxon table, an Aerotech
ballscrew slide, A bracket for a Kress router and the router itself.
I also have a aluminium based plate and a structural aluminium column.
Things are going quite well, I only started on Monday and now have a
pretty good idea of how it will go together.

http://www.indoor.flyer.co.uk/kt150mill.jpg

I do however need some advice on the motor mounting and leadscrews.
The screws are 10mm ACME with a lead of 2mm. They run in brass/bronze
nuts which are quite loose fitting. The shaft passes through a collar
before exiting the extrusion to go into the handwheel which is
attached by rolled pin.

As it stands I am happy with the bed but the screws have far too much
backlash and the use of washers as bearings is not great either. I
need to get rid of the backlash and stiffen up the bearing
arrangement. I'm not sure if the best bet is to replace the screws or
make new nuts or ebay some ballscrews.

Some pics of the leadscrew arrangement here:

http://www.indoor.flyer.co.uk/leadscrew.jpg
http://www.indoor.flyer.co.uk/leadscrew2.jpg

Any advice appreciated.

Cheers,

Graham