Fences come down in the wind for one of two reasons: the posts were not deep enough, or the posts rotted at ground level. Everything above ground is the part you look at; the part that decides whether it lasts is the 600mm you cannot see.
So posts go in deep, in concrete, with the ground level detail done properly. On exposed runs — and anywhere catching the wind off the Solent qualifies — we will talk to you about concrete posts with timber panels, which gives you the look of a timber fence and takes the rot problem away entirely.
Everything is built on site to the run you have actually got, so a fence that has to step down a slope steps down neatly rather than leaving triangular gaps at the bottom for the dog to find.