u/Ali80486

Source image is from 2022 but its not changed much. The dividing line is basically the East Coast Main Line.

Some (old) notes from gov.uk

In 2021-22, 2% of new residential addresses created were within the Green Belt. This is unchanged from the 2020-21.
In 2021-22, 51% of new residential addresses created within the Green Belt were built on previously developed land. This is an increase on the 47% recorded in 2020-21.
In 2022, 6.8% of land designated as Green Belt in England is of developed use with 93.1% of land of non-developed use.
Of land designated as Green Belt, 0.3% is of a residential use with residential gardens accounting for a further 2.9%.