An electrical switch assembly for an electrical appliance, the appliance including an electrical load, comprising: a housing that is substantially cuboidal and has a plurality of sides and external walls, including a first external wall having an opening occupying almost all of the side of the housing that includes the first external wall; a plurality of switch terminals (T1,T2,T3,T4) comprising two input terminals (T1,T2) for connection to a power source and two output terminals (T3,T4) for connection to said electrical load; a mechanical switching module located within a first part of the housing, said switching module comprising at least one fixed contact and a moving contact supported in the housing for movement between a first position in contact with said at least one fixed contact to switch on a said electrical load for operation and a second position out of contact with said at least one fixed contact to switch off said electrical load; an electronic control module and a semiconductor switching device located within a second part of the housing, said electronic control module being operable with the semiconductor switching device to control the operation of said electrical load; and a heat sink located within the second part of the housing, said heat sink being in thermal contact with the semiconductor switching device for dissipating heat of the semiconductor switching device; characterised in that the housing comprises at least two distinct first and second parts (110, 120), the first and second parts (110,120) of the housing comprise separate and distinct compartments of the housing that are separated by a third part of the housing comprising a partition formed in the housing, the partition including opposite first and second sides configured for connection with the first and second housing parts (110,120) respectively, and wherein said first and second parts (110,120) of the housing are able to be detached from connection with the respective first and second sides of the partition for replacement; and the heat sink being configured for closing the opening in the first external wall and forming a major part of the first external wall, and wherein, the heat sink is electrically conductive so as to form an output terminal of the electrical switch assembly and which is also configured for electrical circuit connection with a first terminal of the mechanical switching module via the electrical load. a housing that is substantially cuboidal and has a plurality of sides and external walls, including a first external wall having an opening occupying almost all of the side of the housing that includes the first external wall; a plurality of switch terminals (T1,T2,T3,T4) comprising two input terminals (T1,T2) for connection to a power source and two output terminals (T3,T4) for connection to said electrical load; a mechanical switching module located within a first part of the housing, said switching module comprising at least one fixed contact and a moving contact supported in the housing for movement between a first position in contact with said at least one fixed contact to switch on a said electrical load for operation and a second position out of contact with said at least one fixed contact to switch off said electrical load; an electronic control module and a semiconductor switching device located within a second part of the housing, said electronic control module being operable with the semiconductor switching device to control the operation of said electrical load; and a heat sink located within the second part of the housing, said heat sink being in thermal contact with the semiconductor switching device for dissipating heat of the semiconductor switching device; characterised in that the housing comprises at least two distinct first and second parts (110, 120), the first and second parts (110,120) of the housing comprise separate and distinct compartments of the housing that are separated by a third part of the housing comprising a partition formed in the housing, the partition including opposite first and second sides configured for connection with the first and second housing parts (110,120) respectively, and wherein said first and second parts (110,120) of the housing are able to be detached from connection with the respective first and second sides of the partition for replacement; and the heat sink being configured for closing the opening in the first external wall and forming a major part of the first external wall, and wherein, the heat sink is electrically conductive so as to form an output terminal of the electrical switch assembly and which is also configured for electrical circuit connection with a first terminal of the mechanical switching module via the electrical load.