My wonderful gas fire isnt working!!! I put a new gas bottle on last weekend and it seemed faulty cos the fire wouldnt work, so I took it back, they let me change it and it was fine. Anyway, its been fine all week. But tonight when I went to switch it on, it wont stay on! The pilot light comes on, but it makes a crackling sound and when I take my finger off the other button it just goes out!! Any tips??? Its cold!