Rivet Joint said “Begs the question why the bigger airports stick with ILS though?”
The answer is lower minima for ILS.
With the greatest respect to other posters, I don’t have to check out SOU approach plates or links to explanations of types of approach or consider the lack of LVPs at SOU.
The question was “why the bigger airports stick with ILS?”
The answer FOR BIGGER AIRPORTS is that the ILS allows operations to continue in marginal weather - in fact right down to 0/0 if aircraft is so equipped and crew are suitably qualified.
Apologies for the lack of Southampton references here but I was simply trying to answer a question from another poster about bigger airfields.