Triton Cartridge replacement.
The cartridge was fitted in a remarkably short time, everything fitting perfectly with no leaks.
Unfortunately, however, temperature control spindle (plastic) sheared on first use. (I believe there must have been a manufacturing flaw)
The Shower Doctor offered to replace it immediately, but, not wishing to drain my system a second time I repaired the spindle with superglue. With care it will last well! I nevertheless purchased a second cartridge to keep as a spare.
The Shower Doctor's service has been excellent throughout.