My type of vent:

..and another view, also showing the 'fly screen' that needs to be fitted between vent and panel:

Bought this of the bay of fleas (from an idea on here about refitting door seals


Taped all around the inside edges of each vent:

Holes marked where the screws will go (not necessary but helped to relocate the fly screen correctly):

Fly screen in place:

Followed by a second layer of tape all around edges:

Close up shows double thickness, and I intend to leave the 'cover strip' on the tape when initially refitting the vents (whilst paint is fully hardening) which solves the problem of having to cover the holes from the weather at the moment:

Seems to be a quick, clean and easy way of doing it but nonetheless I'll be keeping a close eye on the vents etc to ensure it's fully leakproof.
Must now get some of those vent covers too
