Hope your well, thanks very much for the reply. Been thinking about this for a while and have suspended work until i know what to do next for sure. I think what your saying makes perfect sense. I would like to put up a wall infront of the pipe but like you say this relys on there not being a problem with it-ever, so its a bit of a gamble. Its all still abit confusing to me at the moment.
Im thinking maybe after what you say, the best option is to make a stud wall with dense rockwool inside and put the channels, green glue and boards onto this. This would reduce the direct sound onto the rear house wall as well as isolating it further with the channels and glue.
For the ceiling ive put in 100mm dense rockwool and plasterboard over this-i will be adding another layer of board then will treat the ceiling the same as the walls ie with battens, more rockwool, channels and double plasterboard all sealed with acoustic sealant. Do you think this will be sufficient to reduce the flanking from the ceiling into the new stud wall?