As for the “smartening” of the fan with a separate smart switch, an important factor might be space. European wall outlets are usually smaller than American ones. So if there only is one of the standard outlets with 74/70mm diameter adding a separate switch might not be an option and I’m not sure if there are smart dual switches to fit in one of these.
But smartening the fan itself with a Photon, a non-invasive sensor and a solid state relay shouln’t be too much of a problem - the tricky bit might be to make a neat integrated power supply for the Photon.
@peekay123, another possible setup might be that the master is the light and the slave is the fan (which has it’s own power line) - but @ltpitt may need to clarify, what it actually is.
One common, cheap, non-smart delay setup is that you switch on the light, which also powers a secondary (hidden) switch which has some bi-metal “override” contact to keep the fan power on after the light is switched off till the bi-metal has cooled down again and subsequentially opens the override too.
With a similar setup (two hot wires) smartening a fan the way @ltpitt imagines should be fairly straight forward.