My St George Electric oven keeps turning itself off.

since I have no model or serial, I assume this is an electric oven based on the description provided. this is usually an indication that the heating element has gone bad. possibly having a short to ground which completes a partial circuit in turn giving you heat and a light. I would look in this direction first.

Most oven doors can be removed by opening door and pulling straight out. The hinges are attached to the oven frame not to the door. Some oven doors have screws that are attached to the hinges at the bottom of the door on the inside that need to be removed, then pull straight out.

Can't find your model # but maybe this can help:
St. George Oven Manuals

Hi there i have the same issue. any results?

I have a St George glass cooktop with temperature sensor light.It takes forever for the light to go out when I use the main element and that section often feels like it is still heatinglong after it has been turned off.Can there be power leakage through the switch for the main element

check wiring to cavity air pressure switch terminals eg the two wires should be connected to common(c) and Normally open (NO)

I have this exact same oven and this "feature" annoys me no end. To turn it off ... turn the clock dial to PAST the time that the timer dial shows. EG: If your timer dial is showing 6, turn the clock dial so that it rolls past 6 o'clock. This will pop out the timer dial and thus turn off the timer, allowing you to use the oven normally.

To stop accidentally pushing/turning that timer dial, I removed the knobs. Good luck.

green is always grounded

Try espares. Once you have the part number, google the part number to see who else can supply.

http://www.sga.com.au/User-Manuals/default.aspx

Anyway that will get you to the right people.