Basically this is what I have to deal with, sorry it's so dirty, no point in cleaning it until I know it works!

I have the gas switched on, I know that because my hob and grill work perfectly, but I can't get this to ignite whatever I do.
I have turned the dial to 3, am holding it in, press the igniting button (yes Im sure there is probably a proper name for this but I can't think of it) and looking through the little peep hole. Now I can see a spark but no flame igniting. Am I doing something wrong?
Also what does it need to be on to work off the 12V leisure battery. I know how to switch my battery on from the control/panel box thing so that's not a problem, but not the flipping fridge.
Any help please, short of throwing it out?
Thanks very much, kellye x