Last week or so, radiatiors occasionally have been staying on, even though Room Thermostat is set low and c/h programmer switched to H/W only. Checked lever on motorised valve when system powered off and there is resistance to move lever to the right and it returns to the left again. System is currently behaving itself heating h/w only. Asked local heating engineer and he says the honeywell motorised valve probably needs replacing and quoting me £150 to replace it . Says the whole system will need draining down. Do you think this is a correct diagnosis and what about this cost? Thanks for your time.