Siemens Oven - light not working but oven all ok otherwise???

Hi, I have a Siemens Single Oven HB75AB550B. When I turned it on last night, there was a flash/pop inside, and the 20A mcb fuse tripped in the mains box. I assumed it must be the bulb (yes it was blown), so replaced it with a new one, reset the fuse, and reset the oven clock.

All seemed ok, the oven appears to work fine, but the light doesn't come on. I tried a second bulb (both are good) with no luck. What could be the problem?

Note that the fan works, the fan element, bottom element, and grill elements all work. When I switch to light only, there is a relay 'click' but no light. I've pulled out the bulb socket unit and checked the wires - all 3 (2 + Earth) are attached, and clean. Socket is also clean.

Is there a fuse inside just for the light? Or is there something else which would stop the light coming on? I'd be grateful for any help.