From Aylesbury, and looking for some help

[Lord Kitchener]

Maybe make it so that you can easily put the base panel back on the machine to take a tiny bit off untill it fits?

It depends on whether it's still parallel- the accuracy is not just for ease of fitting the parts together, it's also needed to sure that the opposite edges are parallel, so that the compononent has all four corners at right angles.

Surely you would plane the proud part down, not sand it. Shouldn't take long to plane off a mm or so.

A decent random orbit sander is faster, and the discs can be changed quickly when they wear out. Planer blades would ned to be TCT as the material can be quite abrasive

Have you considered making a complete CNC router ... then you can make it cut the holes rebates etc automatically.

I have certainly thought about it, even been tempted once or twice. Holding the material down would be a problem, birch ply does not lie as flat as most kitchen cabinet materials, and a powerful vacuum pumo and system would be needed. There's also the issue of needed to learn quite a bit of software, whereas at the moment I can keep most of the numbers I need in my head, and the 8'x4' sheets to cut down in a quite logical sequence, and if one of the boards has a nasty knot in it I can easily cut around it to avoid it.

One fo the nice things about a machine such as I described in the original post is that I would be working with digits on a screen, rather than having to read a scale, something which I have a problem with, sometimes.