I've now got my Greenstar HE28 System boiler installed (thanks John!).
Unfortunately, as it is connected to a heat bank, I need the flow
temperature to exceed the normal 75C limit. According to the
installation/commissioning manual, this is done by removing the yellow end
cap from the temperature selection knob and reinserting it 180 degrees to
the original. Unfortunately, it doesn't seem to want to budge and I don't
want to apply more force than I am, as it might snap the PCB/knob. Has
anyone ever been successful in this task? Any ideas?

Christian.