I have the same problem. The John Sydney brand is now owned by Britax but they don't seem to have any technical knowledge left from the old firm.
I tried by taking the ceramic tap "Hot" button off but found it had been glued to a flat on the knob. No screws there, and hard to glue back on.
John Dalton
March 2021
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix plumbing.