Flashing green LED on Potterton Suprima 50?

Central heating stopped working last night. Tried resetting unsuccessfully.
When reset button pressed the pump starts going, then it sends 240v to the fan motor, but it just makes a burrring sound and doesnt rotate and the green flashing LED comes back on.
i thought i would be clever and gently suck on the air differential tube to trick the pcb into thinking it was spinning just to prove it was motor failure, but the system still didn't kick in? The spindle spins freely when the power is removed. Is it the motor at fault, and if so how do you replace them?