This may be common knowledge to everyone else, but I only just found out that British Waterway/Canals & Rivers Trust keys are available on ebay.
I always find it frustrating that the water taps on canals are kept locked up. I'd always assumed that you would need some sort of boat licence to get one, so it was a nice surprise to find that for under £3 I can add canal boat moorings to churches as a source of drinking water.
I'm not aware of a map showing all their locations though. There's this one, showing canal services, but it's not really relevant from a cyclist's point of view.

My parents have a narrow boat so iv had a key for years however iv never really had to use it as iv always found them to be open. Well the ones iv used in past. Earlier this yr I was up in Scotland on the crian canal ( which I can highly recommend as part of a route its stunning) and the lock keeper even said I could use the showers if I wanted to. However I have also come across some right miserable lock keepers also like the one on the stoke pound flight near Bromsgrove!

Hmm, never really thought about that, but a handy nugget of information .

I happen to have purchased a disabled toilet key coz they were a couple of quid on Amazon and can think where that might be handy!

I have lived on boats for the past few years, yeah it can be mega handy if you need the bog too.
having said that most of them are already unlocked and the taps can often be craftily opened if they are locked.

there are even some canal short cuts that get gated-shut after dark (gotta be respectful if they are also moorings though)

Handy to know, thanks.

Seeing as they've provided a very detailed image of said key, you could make your own