Thanks for your reply @Redbeard Yes sorry, I wasn't aware all the pictures were going to be posted hence the lack of explanation.
I have spoken to the cladding team today who said a bespoke gutter could not be fitted where the red line is due to it being a flat surface so the water may sit and cause more issues. My neighbour does not want normal guttering to over hang into his airspace as he is selling his property and doesn't want to complicate things!
The garage doesn't share the same wall but is built very close to my property many years ago - I assume this would not be allowed now!?
I am hoping there may still be a bespoke solution that could sit on top of the ledge and not interfere with his airspace.
Thanks