As the "central" number for the UK Police Force's is 101 it's difficult to search for alternatives on the database using 101 as the number due to us not having a section for 101.
I typed in Metropolitan Police (Met) which is the main Police force for London and the number shown was the alternative 020 number for them.
Perhaps we could look at having a dedicated page for 101 alternatives?
I agree that the Police UK page is good, but it does mean you have to know to look there.
I personally keep the 020 number stored in my phone for the Met, but it's each to their own.