One reason to avoid three phase is for premises open to the public, and subject to local authority inspection.

Some local authorities have an irrational fear of three phase. I recall a case in which a busy pub installed an outdoor, 3 phase, 16 amp ceeform socket outlet for an ice cream machine.

The local authority were horrified that a "red for danger" socket outlet that used "high voltage" had been installed without consultation, in an area used by families. It was removed rather than enter into an argument.

I have also heard the objection made that the mating plugs "do not contain safety fuses"

One reason to avoid three phase is for premises open to the public, and subject to local authority inspection.

Some local authorities have an irrational fear of three phase. I recall a case in which a busy pub installed an outdoor, 3 phase, 16 amp ceeform socket outlet for an ice cream machine.

The local authority were horrified that a "red for danger" socket outlet that used "high voltage" had been installed without consultation, in an area used by families. It was removed rather than enter into an argument.

I have also heard the objection made that the mating plugs "do not contain safety fuses"

broadgage said:

The local authority were horrified that a "red for danger" socket outlet that used "high voltage" had been installed without consultation, in an area used by families.

Well, I can see this argument ... but it would also apply to 16 A single-phase BS EN 60309-2 socket-outlets (among others) ... i.e. not shuttered.

Cue discussion on whether an outlet with an interlocked rotary "isolator" would do ... yes, but only if the isolator was actually an "isolator" - and all the BS EN 60309-4 products I've come across so far are not marked with the "isolator" symbol and therefore only contain interlocked switches, not interlocked isolators.