I've balancing my new CH - noticed the flow and return to the boiler
were virtually the same - and the auto bypass valve was set to minimum
(0.1 bar = 1m head water IIRC)

Closing it down to 0.4 bar has jumped the differential temperature - but
I suspect that's too high.

The Worcester manual says the pump can deliver 2m head for "21C
temperature rise" - nothing else about min flow rates or bypass pressure.

Any ideas? If I turn it to 0.2bar the flow temperature starts to creep up.

Now this may also suggest I have the lockshields all turned down too low
as well (I've opened 1/4 - 3/4 turn as a starting point).