A method of establishing an electrical connection through a flexible planar material, the method comprising: attaching an intermediate coupling element directly to the flexible planar material; and coupling an electrical connector to the intermediate coupling element, the electrical connector being a first part of an electrical connector assembly, wherein: the intermediate coupling element comprises a frame portion defining an aperture; said attaching comprises aligning the aperture with a hole through the flexible planar material; the intermediate coupling element and the electrical connector comprise a mechanical coupling mechanism allowing removable coupling of the electrical connector and the intermediate coupling element; and said coupling comprises removably coupling the electrical connector to the intermediate coupling element from a first side of the flexible planar material, characterised in that: said attaching comprises sewing the intermediate coupling element to the flexible planar material; and said coupling permits an electrical connection between the electrical connector and a removable second part of the electrical connector assembly, through the flexible planar material, when the second part of the electrical connector assembly is mated to the electrical connector from a second side of the flexible planar material opposite to the first side of the flexible planar material. attaching an intermediate coupling element directly to the flexible planar material; and coupling an electrical connector to the intermediate coupling element, the electrical connector being a first part of an electrical connector assembly, wherein: the intermediate coupling element comprises a frame portion defining an aperture; said attaching comprises aligning the aperture with a hole through the flexible planar material; the intermediate coupling element and the electrical connector comprise a mechanical coupling mechanism allowing removable coupling of the electrical connector and the intermediate coupling element; and said coupling comprises removably coupling the electrical connector to the intermediate coupling element from a first side of the flexible planar material, the intermediate coupling element comprises a frame portion defining an aperture; said attaching comprises aligning the aperture with a hole through the flexible planar material; the intermediate coupling element and the electrical connector comprise a mechanical coupling mechanism allowing removable coupling of the electrical connector and the intermediate coupling element; and said coupling comprises removably coupling the electrical connector to the intermediate coupling element from a first side of the flexible planar material, characterised in that: said attaching comprises sewing the intermediate coupling element to the flexible planar material; and said coupling permits an electrical connection between the electrical connector and a removable second part of the electrical connector assembly, through the flexible planar material, when the second part of the electrical connector assembly is mated to the electrical connector from a second side of the flexible planar material opposite to the first side of the flexible planar material. said attaching comprises sewing the intermediate coupling element to the flexible planar material; and said coupling permits an electrical connection between the electrical connector and a removable second part of the electrical connector assembly, through the flexible planar material, when the second part of the electrical connector assembly is mated to the electrical connector from a second side of the flexible planar material opposite to the first side of the flexible planar material.