I have altered the right rear brake line to accommodate the handbrake cable if it requires to be changed out in the future (shouldn't ever need to?).
I think this gives enough room for everything required, and it still neat enough not to get in any things way.
I still need to finally bolt the tee piece into position using an M6 bolt, but I will also put on a P-clip to hold the main handbrake cable that runs from the handbrake lever.
The handbrake cable is too long so I will have to investigate how short I need to cut it. I have seen some people using splice crimps, but I am going to look into remaking the end that goes onto the calliper itself. I'll keep you posted.