Is this mould on my plaster?

No, bridging in the above sense means: is it transmitting moisture across the cavity - CWI is not supposed to do that.
There's masses of info on the internet about the failure and perils of CWI.

Whatever i suggest is the best info i can give you from my working life experience - whatever you choose to do with the info is, of course, up to you.

All of it much appreciated too, ill have to try and sort this area out best i can at the moment. If i get back to work ill go into it further a step at a time
Thankyou so much.
Sorry forgot to add is this Talc a dangerouse mould.

I don’t see any mould in your pictures.
In the second pic, I can probably see salts/minerals that have been carried through the wall by damp.
You obviously want to fix this. But it is not “dangerous mould” as far as I can tell.

Ok thank you these are the bathroom pipes both seleant looks ok in place lcant reach to check by touch. Ive used the bath lots since this and its still dry. Im almost sure its rain now, ill have to wait for a bad rain fall again. Nothing i can see outside. I did reach out and apply sealant along the top window ledge a few weeks ago just incase

Just painted the full outside wall, and resealed pipes etc.
Found above the soil pipe there was a gap enough to allow a small amount of forced rain in. Lower down the soil stack bolts ( original are the cause of a cracking area) all sealed up now.
I also noted there is 2 old cistern pipe that doesnt exit into the bathroom 1 high cistern and ither sink hieght so ill try to fit an end on the lower obe. I cant reach the higher one hopefully it will stop any rain being pushed in it.

However Since i reached out and filled the upper window sealant gap i havent seen any patches. Theres no crystals back yet either.

I have 2 new glass units being fitted at that window so ill ask if they can redo the sealant aswell.

Ill watch the inner wall through the rainy months then ill tackle the plaster thats damaged.

Now ive painted the exterior wall well. It was sprayed over the terylene 10 years ago very thinly and loads of gaps like honeycomb all over. Im filling it all in carefully and taking my time.
Inside im lifting off the top plaster to monitor any more damp before smashing away at it..
Ive hit the plaster its going to be a devil to smash off its very solid.
The skims off in places but thats also stuck fast to.
Im going to dig out the major cracks ive been bodging paint over these for years, to see if they show water. There is a gap from cieling to wall where a drip of water came down through last year. I havent seen it again since.
Im also removing the bath panel tomorrow just to check the water away outlet at the cavity even though it seemed ok on the outside.
Failing this the carpet will come up by the wall in the room above and a few floorboards to check no pipes are leaking. Theres not many there but i need to check.