Halstead Ace Boiler, Power Light Flashing?

I have a halstead ace Boiler, When i demand hot water or heating i can hear the boiler fire up, then it stops and the green power light flashes.
Someone told me the pump has probably gone. I have checked that there is 240v going to the pump with a meter and i have removed the end cap and used a screwdriver to see if it turns, seems to turn ok
Anyone know how i can fault find this before i go and buy a new pump at £100