That’s very helpful, many thanks for the advice.Yes, pump runs during anti-cycle to stop overheating in the heat exchanger. Wider delta T is more difficult to acheive as the boiler modulates flow temperature as the 'headroom' reduces. A slower pump would help but it wouldn't be much difference to fuel costs.
It’s not easy for a lay person to know what’s going on with how the electronics is designed and the parameters that determine what it does.