As this is a commericial catering establishment. I would assume the supply is three phase.
As the OP wants to put all three units on one circuit (I am assuming they are next to one another). Then I'd put forward the suggestion of one 16A ceeform socket on each phase of a 16A three phase circuit. SWA into adaptable box, few DIN rail terminals with links installed for the neutrals and earths then out to three adjacent interlocked SPN 16A sockets
Done similar arrangements with site cabins when distance was an issue and needed to be eccomical as possible with cable sizing
This issue would be covered by PUWER98, in which case it is doubtful that those sockets would be suitable as emergency means of isolation of energy anyway, so, something else would be required by statute law.