I'm a little confused as to what was actually used in the UK before standardisation on BS 1363 for domestic installations.

BS 546 seems to have been a really impractical system. I've seen it in use in Ireland in a few homes wired during the 1950s (during later days of rural electrification schemes etc).

3 sizes of plugs: 5amp?, 10amp? and 15 amp..

Some rooms had 5 amp outlets, some had 10 amp and the kitchen etc had 15 amp. (Some rooms had combinations of all 3.. 5 amp for radio/tv/lamps etc and larger ones in "general" areas)

It meant that you needed endless adaptors to plug small plugs into big sockets and that you couldn't just plug the radio in in the kitchen or move the TV or even vacuum without huge extension cords!
(at least our old schuko installations weren't that complicated)

I've also seen homes/public buildings with only the huge 15amp sockets. (the type that required 2 strong guys to unplug anything from and usually cracked the sorrounding plaster work [Linked Image] ) They were common place in schools built in the 1950s right up until the 1980s usually dull brass wallplates. [Schuko wasn't too popular after WWII (I guess lack of german imports/change in attitude toward germany for a while!)]

I've also heard that the current Australian standard is based on an old British system? Is that true? Perhaps used on obselete DC installations or something?

Was there a British non-grounded plug (other than the shaver one)? I'm sure i've seen a plug that looked like BS 564 with no earth/ground pin. Big black round wall plate with 2 large round "holes".

Why did Britain use so many different plug types? Seems to have been an unnecessarily complicated system.