I have noticed some of the paint on the outside of my window frames is
starting to blister. I remember when the windows were installed they
made a thing using about using microporous paint.

Does this mean I need to use microporous paint again?

If so, can I buy microporous primer, and is this needed?

Could or should I just rub it down a bit and use exterior paint?

Is water-based paint any good for outdoor use these days or should I
be looking for oil-based paint?

Could I use the paint Network Rail used on the Forth Bridge :-)