Thanks 99. i took The thermostat out, ( it works properly but I cleaned it anyway) reverse flushed the motor, put it back on the muffs and all good. There must have been a blockage somewhere. Anyway, went out again yesterday and it ran perfectly, 2°c cooler than it had been doingsome motors do not like muffs, cannot get enough water.
or stat stuck closed or poppit valve stuck open if that motor has one