No "cups" in old British recipes I've made but there will be measures
  you have to look up like a "gill".

https://oldbritishrecipes.com/collection-of-old-biscuit-reci...

And yeah, depending on how far back you're going or what sources you're using, there will be a lot of vaguely defined quantities. Glen of Glen and Friends on Youtube regularly cooks vintage recipes and gets into how things evolved over time. Most of his old cookbooks are either Canadian or American but from time to time he cooks from UK cookbooks.

I'm sure there will be examples and my childhood memories won't be great but that link isn't a good example of British recipes.

Most of the instances of "cups" come from the "Edwardian recipes" which is a collection of international recipes including American. It includes in the preface a Table of Measures which is what you do for Brits who see "cup" and ask "what the fuck is that?"!

4 cups flour = 1 quart or 1 lb.

2 cups of butter (solid) = 1 lb.

2¹⁄₂ cups powdered sugar = 1 lb.

1 cup = ¹⁄₂ pint

1 glass = ¹⁄₂ pint

1 pint milk or water = 1 lb.

9 large eggs = 1 lb.

1 table-spoon butter = 1 oz.

1 heaping table-spoon butter = 2 ozs.

Butter the size of an egg = 2 ozs.

https://www.gutenberg.org/files/68137/68137-h/68137-h.htm#Li...

It's notable with that link that old recipes mostly used weights for the ingredients and only a minority used cups