HOW CAN I FIX THE IGNITION SYSTEM ON MY CANNON GAS COOKER?

I HAVE A CANNON STRATFORD FREE STANDING GAS COOKER. THE IGNITION SYSTEM IS FAULTY. I HAVE TRIED REPLACING THE BATTERY WITH EVERY TYPE & MAKE OF BATTERY, THE IGNITION WORKS FOR MAYBE ONE OR TWO CLICKS BUT THEN THE BATTERY BECOMES EXHAUSTED. SOMETIMES THE REPLACEMENT BATTERY, ON INSPECTION, IS SWOLLEN & DAMAGED. THE COOKER IS 6 YEARS OLD. THE IGNITION HAS NOT WORKED SINCE FIRST BATTERY WAS REPLACED 5 YEARS AGO.