Right I'm just off the phone to planning and they are sending someone round tomorrow. They sounded very concerned. I have also done a bit of digging around on the plannings website and there have been several applications for external work (not by NDN) for flats further along in the same building. It's for things like light fittings and extending a door. All of these applications have next to them "application refused" or "refuse and enforce" so there's not a chance they're going to get away with this.
I'll try to answer all the questions sorry if I miss any!
Yes the doors clearly open outwards in to the garden.
There isn't damage to my garden per se it's just a mess now!
It's those white flimsy cheap looking patio doors that have been put in. It was a lovely (very old) curved sort of window with the black out doors either side (I know there's a name for it, can't remember right now)
I have no idea if they have affected the structure although I wouldn't be surprised. They've destroyed the original brickwork so even if it does need to be rebuilt there's no way this could be used. It's all smashed and broken 
AHHH IM FUMING!!!