Why the residue looks different here
Efflorescence, the powdery white deposit that shows up on paving, is caused by moisture drawing salts up to the surface as it evaporates. Around Broadstairs's chalk bays, salt-laden sea spray mixes with fine chalk particles carried off the cliff faces, so the film that builds up on a patio is often paler and more powdery than the darker salt staining seen on shingle coastlines like Deal.
What actually works, and what doesn't
A light wash with clean water reduces the visible white bloom, and once the salts have finished leaching out, the problem often eases on its own. The right approach depends heavily on the slab: porcelain and concrete slabs handle a proper pressure wash well, but soft natural stone such as sandstone can be damaged by high pressure and needs a gentler, lower-pressure pass instead.
Technique that avoids striping
Starting with a fan nozzle rather than a pinpoint jet, keeping pressure on the lower side, and holding the lance at a shallow angle while working in steady overlapping passes avoids the striping that a rushed pinpoint blast leaves behind.
When to just wait
New efflorescence on recently laid paving is often temporary. If a patio was laid within the last year or two, a lighter clean now followed by a proper wash once the salts have stopped leaching is usually the better call than an aggressive treatment straight away.
Sources: Marshalls, "How to Clean Your Patio Slabs"; Minster Paving, "How to Clean Patio Slabs".