My boiler is continuously cycling on/off for 10s periods; stop this?

I have an Ideal C95FF combi-boiler which was working fine although not all of the radiators heated up to the maximum. Bled a couple of them which went fine. But now my boiler is cylcing on/off every 10seconds or so. It doesnt matter if the control switch is on/off/timed does it automatically. How do I stop this?