It's an eye opener for me and tbh I only even looked as this juncture because of what I've learnt on here. Makes a mockery of the whole concept of "double glazing". I can imagine DG fitters on a price doing the same with TRIPLE glazing   As I say making the best of a bad job!   Foaming around the window just now makes the gale coming up through the cavity even more noticeable! I masked the edges with tape so I can cut it level when set: