I had printed some idler wheels, bored them to size and then fitted bearings.

unfortunately due to how thin they are and the stress of having the bearings pressed in, 3 out of 4 split

so I decided to try some penny washers instead

These seem to work just fine, my total cost for the 4 idlers including the bearings, nuts, washers, etc as well as the cost of the failed prints is £1.91, nearly half the price of just a single Delrin idler kit - this method also works just fine on my 3D printer.
I made some more progress on the mechanical build once my Makerslide arrived.
I was able to assemble the gantry and fit all of the Z axis parts.

The stand-offs are brass M3x25mm (£3.15 for 25pcs inc P&P from ebay).
You can also see the M6 cage nuts I used in place of the floating PEM nuts (M6 floating PEM nuts seem to be either silly prices, or need to be purchased in quantities of 1000+), this method was free as I have hundreds of them from installing servers in racks over the years.
I bought a couple of different sizes and also used some on the X axis.

Y axis motor, the smooth 6mm rods were salvaged from some scrapped inkjet printers

I swapped which side of the mount I placed the Y axis motor as one rod was longer than the other, I could keep the piece of 20x20 profile near the middle and not need to cut either of the smooth rods.
High voltage power supply fitted

This is the frame with all belts, end stops, feet, etc fitted as well as the rotaty axis in place (still awaiting a pulley)

I also have my skins, already cut to size, although I still need to drill all of the relevant mounting holes and make any required cut-outs.