fixing faults and obtaining spare parts?

I have a Rosieres Bocuse double oven No. 91138040
Model 2040 c DB GB approx. 27 years old. Circa 1990.
I need a lower element for the right hand side oven
part no. 93386829. 2.8kW.
I also need help with the left hand oven (the windy one) The thermostat governing the grill element does not cut in until around no.6 (half past on the clock) although the fan comes on immediately. So I deduce the thermostat is faulty?
Also when trying to engage the fan element by turning the knob right round to the grill symbol the fan comes on almost immediately coupled with the heater
disengaging.
The only way to maintain the heater 'on' is to
manually pressure the switch to keep the fan off.
Obviously this is not satisfactory and I wonder if the switch gear is at fault - or simply the thermostat?

Another thing - The right hand oven door does not close properly and needs new springs. Where can these be obtained and then how can they be fitted? They seem very difficult to remove - let alone re-fit.
Help with these points would be appreciated.