No experience with KT, though I've got 2 British Labs from Double TT, and they share some lines (Drakeshead dogs, Craighorn Bracken, Pocklea Remus, etc.). There's definitely some marketing hype, but no more than with any other kind of dog. American labs have plenty of marketing hype, too. To say nothing of pointing dogs of all sorts, which are chock full of absolutely silly marketing hype, in no small part because pointing dog people are usually the silliest breed of all.
I never really wanted a lab. Didn't particularly like the breed, but I wanted/needed a different type of dog than the spaniels I owned, and I had started hunting waterfowl and wanted a generalist dog, and my wife wanted a Lab. So, I bought a Lab, and chose a British one at least in part based on the marketing (smaller, calmer, quieter, etc.). My experience of British Labs has been so good, and so close to the marketing hype, that I bought a second. And the next dog I buy is also going to be a British Lab. The dogs I've had so far have just been too good, both in the field and at home, to risk a switch to anything else, and if there's one thing that's worth money in a hunting dog, it's eliminating the risk of things not working out.