Good spot. They aren't that easy to photograph because they are always on the move.
Perhaps I'll potter down to Two Tree Island on Friday morning and try to photograph one. I do tend to spend most of my time there in the bird hide which was where the avocets and oystercatchers were viewed. The whitethroats tend to be diving in and out of low scrub beside the path, with their rasping, sandpapery song. The do occasionally settle, as yours did, in quite a visible spot, but they don't often stay there long.