Thanks Armadillo I got that Linkswitch part pinout wrong, and the On Semi part fits as well but there's no Vcc cap on the PCB.
It's a Panasonic oven or designed by Panasonic and re-badged, it looks like it was designed in Japan, it doesn't look anything like the UK designed oven controllers. It's most probably a Panasonic flyback controller and these parts look like they are possible candidates
MIP2E1DMTSCF, MIP2E2DMTSCF, MIP2E3DMTSCF, MIP2E4DMTSCF
MIP2L30MTSCF, MIP2L40MTSCF
They're all 3-pin controllers, pins 1,2,3,7,8 Source, pin 5 Drain and Pin 4 control. No Vcc cap needed and the PCB layout fits the part nicely. So tpowell1830 was right, it is 3-pin.