ps these kits should really come with a health warning
about the drops in temperatures, I will only use mine
now with three kettles of boiling water being added at
the same time - two dead clowns from temperature
shock was a painful lesson.

As you mentioned earlier in your post, I can tell you're referring to life
in the UK I lived there for three years. You blokes have VERY SMALL
water heaters. No wonder you run out of warm water before the fish tank is
full

Here in the States, it routine to have a hot water tank that is 50 gal or
more. Virtually every house has one this size. This makes it easy to fill
a 55 or even 100 gal tank with ~80F water with no problem. Simply adjust
the hot/cold ratio at the water faucet for the right temp before starting to
fill. I love my Python!

-Frank