Probably a stupid question I know, but I have a wall mounted TV in the kitchen and the most convenient place for the digibox would be on top of the microwave.

Would that be OK or would they interfere with each other?

I think a satellite box might be worse to have than a freeview box as its closer to satellite band signals I wonder?

It's a free view box

On the basis that a microwave oven is designed to keep the microwaves enclosed with in the unit there is unlikely to be any ill effect putting the digibox on the top. Provided that is you do not block any ventilation slots there may be in the top panel.

Heat rather than microwave radiation is more likely to cause problems.And if the microwave leaks enough energy to interfere with the digibox you have more problems than not being able to watch telly!