To partially answer my own question, I've just found this on the TLC
website:

"Low Voltage pumps use a 24v supply from a mains transformer and as low
voltage connections require no tools, installation is a straightforward
inexpensive task. No extra cable protection is needed. The cable can be
extended up to 50m. Our low voltage pumps have identical performance to
their mains cousins."

"No extra cable protection" is a little surprising.