The press always hype things up to the fullest and publishing propaganda is their specialty
however there is absolutely no reason why great white sharks do not some times visit are waters, the mako shark which is a cousin of the great white have been frequently spotted in our waters, also sea temperatures are well within their tolerance around the UK. 99% of the time its just a case of mistaken identity when people spot a shark (usually a porbeagle) they automatically think great white! the porbi is also a cousin of the great white and they do look slightly similar and so does the mako. Rare marine life thats not known to live in our waters does sometimes show up, like leather back turtles or tuna fish for instance, so with sea temperatures well within their tolerance and an abundance of food like seals the question is why don't we see great whites in our waters and not is there! i suspect the answer is that visits are so rare that they often go unnoticed and usually if one is spotted there's no one around at the time to make a positive identification.