How can I fix my Glow Worm Majorca 3 Radiant Convector Combined Heating Sys?

A noise like 'phwitt' keeps coming from (I think) the gas jets? My son cleaned them with a paint brush. Also a rocking sound comes from the centre of the fire or back-boiler when the jets switch off and there is a fluttering sound, which I think is from the gas jets just before the flames go off.