How can I fix my potterton peforma 24 boiler?

The boiler comes on but the burner/flame light does not come on at all. The flame fault indicator also does not light up. There is no hot water and no heating. For about 1 week prior to today, I noticed that there has been a small leak from the boiler itself, the pressure is at 1 and once the bolier is on both heating and hot water comes on even though the boiler is only set to hot water only. The thermostat is working but has no effect on making the flame work. Will I need to call out an engineer?