Thanks for your help.
In a moment of sheer idiocy, I was trying to clean ice out of the freezer compartment of our small fridge/freezer (Haier HR-111) with a knife. I made a small hole in the side of the small freezer compartment at the top and gas started hissing out. Obviously I turned the fridge off and removed everything from it.
The question is: is it worth getting the thing repaired or should I just chuck it out and replace it (would cost around 130 pounds) ?