Those threads always worry me because they run a risk of descending some unpleasant slopes, but I'll take it in the spirit of product differentiation and tribute to high end British brands.

From that point of view, BA F arguably showcases a lot of British brands: Liberty washbags, Aromatherapy Associates toiletries, an English sparkling wine which I personally would have preferred to be omitted, China, etc.

In that sense, it seems that the OP question seems to be more about why BA F are not using 'everything' British, but there the answer is probably that because British industry is so small by now compared to many international competitors, it is often limited to a very specific segment, which in many cases might be either of poor quality or very high quality at very high prices.

I'd love BA to invest in Burberry's or Aquascutum sleepwear, for instance, but how realistic is that prospect? If F is about providing excellent brands that the airline can afford, then I'm afraid an 'all British' is probably not a realistic option and on that front, I don't think BA have their balance wrong.