Earthed mechanical protection. Preferably galvanised steel conduit which will need to be terminated correctly to ensure the earth continuity.
SWA is also an option but I personally would still like to see it in a duct of some sort (not necessarily metallic)
I would say the best option would be singles in steel conduit with bends made with a bender as gentle as reasonable to come up into the wall and terminate in the accessories (where it should be terminated properly which will earth it).
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