Night take off from LGW, CAVOK in a BAe146. I called for Gear Up, Master Warning “Avionics Smoke”. Call from Cabin Manager “Forward Galley Fire, ceiling melting”. MAYDAY to ATC. Turned downwind for a visual return at 1,500’ while F/O ran the checklists. Landed in just under 5 minutes. Fire extinguished by Cabin Crew so no EVAC. Source, forward oven fire due grease build up within. Avionics Smoke warning spurious, caused by galley air being drawn down into the avionics bay (as designed). Ovens no longer operated during critical stages of flight in any UK AOC as far as I know.