classic motorcycle forum

Difficulty finding neutral or 1st at a standstill is usually down to a dragging clutch, especially if the gears engage perfectly with a stopped engine.
The suggestion of halving the pushrod and fitting a clutch roller helps with this as the pushrod doesn't then spin with the pressure plate when the clutch is pulled, unlike a one-piece one, which can/does.
You'd get a little more thread to put your locknut on, too..

There's the local Spam enthusiasts club; you might find that interesting.

On your pic of 21st August it appears that it would be possible to screw the clutch nuts down a bit tighter. Have you tried that or do the springs become coil-bound?
Did your dad have the bike running satisfactorily or was the clutch always problematic?
I've had bikes in the past where the clutch springs have measured up OK but still been useless. I suppose that comes with people using what they have rather than buying something known to be suitable for the power expected to be transmitted.

I think you're barking up the wrong tree with that worn clutch centre; if you think it's an issue then simply take a 12" !"£%^% to it and smooth it out. The worst that will happen is that it would rattle slightly more when the clutch is pulled. Hardly a concern.
Usually they're worn much more than that, and the main symptom is a dragging clutch leading to crunchy gear engagement when pulling away.
Don't really see how the minimal wear you have there will/would cause clutch slippage within 50 miles or so.
£330 quid is a bit much for suck it and see diagnostics, too. I'd be looking at plates, springs and something amiss with the assembly first.

Their whole world seemed to revolve around their race to the bottom of cheap and nasty. Price seemed to be the sole criteria for the majority.

"Race to the bottom" is 2020's concept. Theirs was more likely to be "a penny saved is a penny earned" which given the financial hardship of the time, made perfect sense. Profit margins were low to non-existent on bikes made purely for commuting, so every little cheese-paring helped with the bottom line.
You want grease nipples? Buy a Brough, McAvoy, Coventry-Eagle etc etc.

That bog at Bracklesham is a throw-back from the 1950s which is probably the last time it was deep-cleaned. How long can you hold your breath?
I like the bendy road back to the A27 though.

A mate has the identical twin, other than his exhausts are standard low-level.