My GT4 had one H4 light (Koiito original) & one sealed beam (previous owner must have broken the original & bought a sealed beam cos it was cheaper).
I'm not sure about the standard GT4, but on mine (Group A) there is blanked off wiring for fog lights to the corner apertures of the bumper (below the indicators). I'm not sure what fog lights fit in there (maybe the ones off the ST182?), but the holes are only big enough for small 55W lights anyway. They go back to a fuse in the passenger footwell fuse box. Not sure if there's a wire for a switch anywhere.