When I say a phase tester I mean a simple screwdriver type device for checking if a cable is hot or not
(Irish/British term I think!)
As for phase sequence they're quite strict about it here.
Where 3-phase is used each phase is clearly and correctly identified by the cable colour scheme.
The power company would insure that the phase sequence is correct at their meter and the continuity of the colour scheme is simply maintained from there on. There is no question of randomly mixing up the "hots". There is also, like in Germany, a standard way to wire 3-phase plugs/sockets to ensure that the phase sequence is always maintained.
Also where single phase (230V) power is taken from a 3-phase panel it must be wired so that the 230V equipment (sockets/lighting etc) in a particular room is always on the same phase to prevent anyone from being "connected" across 2 phases.
In domestic situations 3-phase is very rare.
Generally a 63-80 amp single phase supply is used.
Electric heating's quite rare here and where it is used it's storage heating so the heating load is on only during the night and would not exceed 63amps.
(90%+ of homes here are heated either by natural gas or pressure jet oil systems) These systems generally heat radiators via a pumped closed pressurised water system. (I've noticed in the UK it's generally open with a head tank)