1.) Apples, oranges, and pears are my favourite fruits.
2.) Apples, oranges, and pears, are my favourite fruits.
Should the comma after "pears" be there (British English)?
No, never! Where did you get that idea from?
There is a rule in Present-day English (all dialects) forbidding a subject and its verb being separated by punctuation.
The only debateable point in your example is whether a comma should come before "and". But that's another matter altogether.