We have a giant hot water cylinder to satisfy my extravagantly sudsy bath-time needs, plus there's only two us and two cats, and the cats never knowingly bathe (though LMC fell in once, she plans to have the forgiveness paperwork completed by 2072). Though my wife never takes a bath either because she's odd ('soaking in your own filth' was her reference to the divine marinadory practice).
Anyway, there's enough hot water that it's never run out, even when we have guests or when someone who looks suspiciously like me with a hangover falls asleep in the shower for twenty-five minutes. Our hot water is generally annoying* though, but I think that's because we have small bore pipes that take a Wonkaesque voyage around the grand state of Surrey before returning to the house. Honestly, the hot water goes downstairs to the kitchen, then to the downstairs toilet, and only then comes back to the upstairs bathroom, which is next to the cylinder. Yes, we would have had the corrected had someone mentioned during the refurbishment. The main shower is connected directly via the sort of pump normally found in riot-control cannons. You could replicate the experience of the back-up shower, in comparison, by holiding a small incontinent kitten above your head.
We do have splendid cold water pressure. If I connect the hose, I can water gardens three houses away.
*ok, it's minor gripe, I can just read a book in the time it takes to fill the bathroom sink with hot water to shave.