yes where on the shower did you get that from it don't tally up with any numbers i've got.
It's on the inside label, label reads
Heatrae Sadia Carousel
Cat Number 95 021 535
Serial 44xxxx
With the cover off:-
Upper right is mains distribution wires.
most of left side is copperesque barrel, I assume this is the heater unit
under the copper barrel is the pipe out to the head unit
bottom middle is the white plastic circle unit the you turn to increase or decrease the temp and as that's where the leak is coming from I assume it's some kind of flow control unit?