Pumo 80 pilot goes out overnight

Have you allowed anything to grow passed the outside of the flue? This can cause wind direction changes that will either blow inward and blow the pilot out, or suck the air away from the flue and suffocate the small pilot flame.

When was the boiler last serviced? Thermo couplings which detect the pilot flame can become weak and not hold the control valve open properly. It might be worth having an engineer look at it for you.

There are a number of other points which can cause these symptoms, but I'll leave at the basic ones.

The fan has to keep moving slowly all the while or eventually the air inside the boiler gets spent and the pilot goes out.

I expect either the slow speed resistor for the fan has gone open circuit or the fan has become stiff and stops rotating when in standby mode.