Years ago a lot of people in the U.K. used to keep all the left overs from the Sunday roast, mix it all together and have a fry up on Monday morning, quite similar to bubble and squeak and delicious.
Oh Yes, forgot about bubble and squeak.
Only heard about it about 10 years ago when travel/cooking shows became so prevalent. Tried it (in Santa Monica California lol), but was assured it was " an" authentic "version". The proprietors were from Liverpool. Absolutely delicious!