Following from my query on track bikes having shorter cranks……so with shorter cranks should saddle be raised a bit to compensate for bottom of stroke ?

Yes.

Cheers Ben

Or no.

Or yes ? Help me !

Depends. Is it at the right height now?

Dunno, in the last month I have ridden at the velodrome about 6 times and on proper bikes 🙂 about 3 times and my dodgy knees are screaming at me. Shoes and cleats are setup perfectly and I’m being careful to not stomp on the fixie so suspect saddle height

It’s not as complicated as the geeks would like you to believe. Extend without hyper extension. Rotate without hip roll.
Knee problems can often be related more to cleat position or shoe fit. Less likely to be seat height IMO.