Well, I got the side off, the left side.* It can be carefully prised off but will probably need to be glued back on.
It seems to be the pressure regulator that is leaking, the leak is not from the place that the pressure is released at the end of a shot but further back in the handle where the pressure regulator is (I think that is what it is). Tried a single shot (no water or coffee) and on releasing the trigger all the rest of the gas leaked out from the top of the regulator (it iced up at the spot it was leaking from). Might try dismantling the regulator and a bit of silicon lubricant but dont have high hopes for it working.
Oh well, might have to buy another one. Makes the best cup of coffee of all my various devices.