You helped me with my issues it was great with no talking down to people.
I have also been looking at posts where you mentioned non return valves maybe at fault allowing passthrough.
So keep doing what your doing Just need to figure out what cartrige i need for shower and how to get it out its jammed in there good. Looks like Rubinetterie expensive one.
He also helped my out MASSSSSSSSSSSSSIVELY to, i wouldn't have it sorted without Picasso's help.