Re: Beko BDV555AS
You ask would you be able to fit a new thermostat yourself, i’m sure you would, but i doubt it would cure the problem, its more likely the oven element needs replacing, perhaps a cut out either.
As for “the front left main job” if it only works on 6 it might need an element replaced too or switch for it.
Hard to say without looking at & inspecting the appliance, but try these points first.
Power off of course when working on it.