In the same conduit - Yes - if its big enough

If you have 2 x 6mm GP (L+N for stove) and 3 x 2.5mm (C.P.C. for stove and L+N for socket) + 1.5mm (for socket C.P.C.) you are at 96 (max 90 on C value on 20mm conduit)

I have seen where guys use manufaturers data and calculate CSA of all cables in conduit and and they still have 40% space - don't like it but have seen it to justify why they passed it.

Same earth condutor for 2 circuits - in a new instal - I'd say no.
In an existing (old) install where your not modifying anyhthing - i believe its a pass (don't like it but....)

If it was already there, I wouldn't make a client rip thier wall apart to change it.