Thnx for your suggestion but finally figured it out. The company had changed the wiring of the actuator, so my re-fitting like for like meant that 2 wires were back to front.
Teach me too look at wiring diagrams properly next time, save having a sore head.
Cheers
I have a geriatric central heating system that likes to regularly play up. Today's problem is that the programmer is not activating the boiler, the programmer is opening and shuting the 2-way valves when asked, but the boiler is just doin a good impression off a cardboard box.
Room thermostat...