The Dingles forget stuff.
Sam inherited a poultry farm in Norfolk when Alice died. Forgotten.
Lisa was a qualified builder and mechanic but forgot those money making skills when it came to filling the Dingle pot with cash to pay their bills with.
They've got form.
Well the thing with the Dingles is that they are simultaneously portrayed as a highly successful business family with interests ranging from (as you say) Norfolk to Scotland, who can outright buy a pub with cash, and also a family living in extreme poverty in a hovel with the same furniture for over a decade who often can’t make the rent and have to resort to poaching and low level criminality to make ends meet.
Belle in particular is the prototype Dingle. Despite being born in a Pigsty to the most...unpromising...of genepools, Zack and Lisa, she is apparently some sort of maths prodigy, and now, from out of nowhere, is also a highly sharp business mind able to easily outwit Al, and probably Kim. Before she has another crippling attack of schizophrenia of course.
And despite inhabiting a village packed from top to bottom with eye poppingly beautiful women, besides whom she is to put it mildly, ordinary. She exudes some sort of industrial strength sexual allure that causes much older professional men such as doctors, vets, or millionaires sons, to become infatuated with her to the point of near obsession or murder. All before the age of 21.
