How can I restart my Potterton Kingfisher II boiler?

Boiler is not working, no hot water or central heating. I turned thermostat up, nothing happens. I don't think the timer is moving (its a dial that you can turn and was recently replaced in Feb when we moved in). I wondered if it needed restarting but we have no instructions. I left the immersion heater on for a few weeks, just realised today, switched it off, then realised boiler not working?? We also switched off the stopcock for a short time today, to try a fix a tap. Would that stop the boiler working. Would be grateful for any advice.