The "full English" (toast, fried bread, grilled tomato, sausages, bacon (not streaky), mushroom, poached/fried/scrambled eggs, baked beans, black pudding (optional)) is not something that is eaten every day. If it was then we would all be as fat as Americans and the island of Great Britain would sink!
Most of us settle for something like porridge, or toast and marmalade, boiled or poached egg and toast, fruit, continental (sliced cold meats & cheeses with croissant or similar), with tea/coffee/fruit juice; and save the "full works" for weekends or even longer intervals.
Don't expect a fair representation of a "full English" in a London hotel. You will just get a small portion of something cheap with missing components, and probably swimming in watery liquid. You won't get decent fish and chips in one either. Hotels in London are interested in profit not the "real experience".
You will get a much better experience of English food (and everything else English) if you stay out of London. It is NOT typical of the country's culture or life at all.
If you are in London then go to a street cafe for a "full English". The sort of small place that taxi drivers use will usually be best, even if they look like "greasy spoon" places from outside.
A 'full English' is a weekend treat for most people, a daily breakfast is more often toast or croissant or cereal or a bacon roll.
I'll hazard a guess that most Britishers don't have a full English breakfast every morning. In many households it would be the Sunday morning treat or saved for high days and holidays. There will be plenty of other breakfast choices on the menu.
If you do try the full English it is only heavy if you opt for all of the available food options. You don't have to have them all. But to get the full experience, whatever your choices on your full English breakfast plate, you must finish with a slice of toast & marmalade.
um, as a tourist, i go ahead and eat the full English breakfast. this usually holds me til the evening meal. sometimes i carry bread and cheese and apples and a pocket knife in my haversack for mid afternoon snack when touring the fine country.
edited to add: i don't stop for lunch when touring, especially in the fall and winter when the hours of operation for the tourist sites are reduced. it gets dark early there in winter.
It certainly is too heavy to eat every morning and only makes sense if you're a manual worker and need the calories. Breakfast cereal, tea and maybe toast is far more normal, or a "continental breakfast" which is what the French do - croissants or bread and jam. Any hotel will have all these on offer, and to be honest, as a Londoner, the only time I ever have a "full English" breakfast is as a treat in a hotel because someone else is cooking it!
You can have what you like.
However, try a full English breakfast. It may be heavy but you won't need to eat again until the evening!
Toast or Muesli or Boiled or Poached Egg. Fruit
You could have toast, or cereal, boiled or scambled eggs,grapefruit,with a cup of tea or coffee, orange juice.
You can have just about any sort of breakfast you like for me it is porridge.