I've been involved with helping Mark via Club-XM forum.
All spheres are now new, and correctly positioned, and system properly bled.
Next step is to have a knowledgeable hands-on assessment of the car.
There appear to be no Lexia's in Wales, according to the list here

except for Paul (citroenxm) in Anglesey.
Suspension electrovalves (and diodes) are likely the next suspect, and probably an idea to fit some EV tell-tale LEDs, so investigation is more conclusive.
Mark would need some help with all this.