Not to ruin the circle jerk but for as much as you can go to Greggs and ignore the Fat Duck, you can also go to Taco Bell and ignore The French Laundry, or Délifrance and ignore Guy Savoy...
Mostly in pubs, but I did try a few places. Carvery buffet, a few different full English breakfast places. Those are the things I'd chalk up to bland but not bad. Brits truly do use less seasoning from what I could tell. Even the takeaway I tried was pretty boring, and all you have to do is fry and salt that stuff.
I don't think your comparison of fast food vs. fine dining is fair. In the US, and the few other countries I've been, "pub food" or family style restaurants are usually always good. They're not high quality but still tasty. I've only been to 7 countries so I'm not super well traveled, but the UK is the only place I've been where I consistently didn't enjoy the food. I can only remember one meal in Serbia I didn't enjoy.
Idk man, maybe you just got unlucky. I just got back from London and all the meals I had were well seasoned - didn't matter if it was a pub, a fast casual place, or a fine dining restaurant.
Parmo was created by Nicos Harris, a Greek American navy chef. He was wounded off the coast of France, and brought to the United Kingdom to be treated at what is now James Cook University Hospital, Middlesbrough.
It largely depends on where you go, and where you eat. It's kinda like saying that I hate American food because I only visited Seattle and ate at shitty shrimp places.
It also depends on what you refer to as "British food". It's essentially comfort food, so you won't find many places trying to do the gourmet version of it without busting your wallet open. The great thing about food in the UK is that you can get food from basically all cultures everywhere (if you're in a city).