On the same theme, I heard recently that a Contractor had installed a Bathroom type Downflow Heater outside of Zone 1 adjacent to a Wet room area as part of a Disabled Persons Bathroom conversions.Contract ...A different Company [NICEIC Members] were contracted to Inspect & Test the instalation when finished, and they refused to pass the job citing extraneous influences on the heater due to the shower head being on a flexible hose...they said the hose could inadvertantly direct water spray onto the heater. The Contractor complained to the NICEIC {NICEIC Knockers can now shout "Who do they think they are ?}. The NICEIC Regional Engineer confirmed the Heater installation did not comply with BS 7671 2008.
Sorry about the long story but it was to illustrate that although equipment is outside of a zone it still may require Ingress Protection i.e. other sections of the Regs are still applicable.