Re: Prince of Wales - been so long since I had it, darned if I recall the flavor, so no help there.
Re: Quality of Twinings on both sides of the Atlantic - OK, I will admit when I read that, my fur went up. I have a knee jerk reaction to what I perceive as snobbery in anything, and that includes tea. (Even if I am wrong.) Since I purchase my Irish Breakfast Blend, loose, from Twinings USA and also have some IBB bags for portability, I thought I'd try them cup by cup. Sorry, I cannot discern a lessening of the quality in either cup, but in using the loose tea, I could make it strong enough for a mouse to walk on. (Old Irish saying from my old Irish great granny.)
If you take a teabag apart, you'll see smaller bits, fannings, and of course there are those whose noses will turn up at that, but the plain fact is that fannings make a lot faster cup of tea without needing 7 minutes or so of steeping time. If I'm using a tea bag, it generally isn't when I'm willing or able to wait a while for my tea to be ready.
Twinings has been in business for over 300 years now. Comparing their longevity with some of our American businesses, their track record isn't too shabby. IMO, neither is their tea. What I have noticed is that often the stock in grocery stores in the US isn't always that fresh. Down where I live, it is easy to find bagged tea for iced tea but not that easy finding another type of tea.