Hi Ken,
I think the plywood used was veneered with Teak, shame we are not able to contact Bruce Parker to ask him! However when I made a new Instrument panel I used a fairly light coloured plywood and stained it with a water based teak stain (Liberon Palette Wood Dye). I then gave it a coat of water based quick drying varnish to seal the surface before a coat of proper varnish. I find if you apply the proper varnish direct it tends to darken the finish, whereas the quick drying varnish doesn't and seals the surface. The result matches the original woodwork perfectly. If you are going to Fareham in a couple of weeks I will show you!
Peter (Zephyr P235)