Why the harbour side is a different job
Properties right along the regenerated Harbour Arm and the beach-facing streets around Sunny Sands get direct salt spray off the Channel, not just the general sea-air staining that affects the wider town. Salt crystallises on paving as it dries, and repeated wetting and drying cycles gradually etch and dull the surface if it's never washed off.
What salt actually does to paving over time
Beyond the visible white residue, salt draws moisture into porous paving materials like natural stone and some concrete products, which speeds up freeze-thaw damage over a British winter and can accelerate the breakdown of pointing and jointing sand faster than plain weathering would.
How often it's worth washing on this stretch
A patio a street or two back from the water might only need a wash once a year. Right on the harbour front or the seafront terraces, twice a year is a more realistic schedule to stop salt residue building up between cleans, particularly after a stormy winter with a lot of sea spray blown inland.
Right pressure for the surface
Concrete and porcelain slabs handle a standard wash fine. Natural stone paving common on some of the older harbourside patios needs a lower-pressure soft wash with a biocide pass, the same approach we use on render, so the salt and grime lift without damaging the stone face.
Sources: Pureseal Services UK, "How Do I Make My Patio Slabs Look New Again?"; DIY Works, "How To Clean Your Patio Slabs".