2004 rienza gas fire heater

Hi, anybody experience on the heater model ?, fitted in 04 rienza ,   its left knob is the adj.stat and the   right knob variable fan one way and electric element fan other way,
ever time want to use have to  take apart and put new battery in it , it appears to be permanently on (sparking) , I though the thermo couple was the the cut off flame device
because fitting new battery in after u turned gas on there a near explosion and have to go look for the top of the cowl ,because you have pressed down the knob to open pilot valve,
 Thats if it has a pilot light system 

PS  in the rehab check does it have to be de fluffed inside the heater,or is it just an advisory like u get in the MOT ?  ,  cost 250£ and full of fluff 

thanks ,