Stuart - I appreciate your kind help and advice.
Next up in the build is the crankshaft - or I suppose crank "axle".
A goodly length of 1/2" mild steel bar is supplied in the kit of materials.
Stan Bray recommends turning it up between centres - "old school". It is turned down each side of the 1/2" central portion, carrying the flywheel.
Here's my set up, starting on one side.

After bringing the bar to size/length, both the centre portion and the outboard end to carry the crank disc were slotted for the keys to hold the flywheel and crank disc.
Here is the axle on the flywheel :-

The crank disc, carrying the crank pin is very plain, and to my eye, looks a bit naff compared to the rest of this quite nice looking engine.
Stan Bray machined a rim around the periphery of the disc to give it some texture. Even so, in the photograph of that, shown in the ME, the disc still looks a bit odd.
There is a substantial boss on the inboard side of the disc, so cutting holes or spokes in the disc is not really feasable.
I decided to see what a "pie slice" crank web might look like, in place of the disc and drew one out full size (roughly!!).
The shading may represent a bit of fluting to add a bit more interest. :-

The disc, proper, is machined from a slice of solid 2" dia. mild steel - a generous length of this being supplied in the kit of materials. Plenty of meat to hold in the three jaw, with jaws reversed :-

It is a straightforward machining job then, to bring it to size and drill/bore/ream the hole for the axle.
This was subsequently slotted for the key to hold the disc on the end of the axle. Both outboard ends of the keyways in the disc and flywheel were carried around into the ends of their bosses so as to take the head ends of the keys (yet to be made).
The hole for the crank pin was drilled/reamed on the mill table using coordinates to get the required 1/2" off-set.
To satisfy my curiosity, I assembled the flywheel/axle/crank disc (no keys yet) and stuck the paper template on the end of the disc, to get an idea of what it might look like if I decided to butcher the disc.

I think I'll sleep on this for tonight and maybe attack the disc tomorrow?
Best wishes to all
Peter