..........When doing low level flight for my PPL, the only place we could use was over water of the Dee Estuary, and even then we had to zoom climb over a pleasure boat.
There is no requirement to fly below 500ft agl for any part of the PPL syllabus and nor should it be necessary to "zoom" climb if the flight was properly pre-planned. Note: A waterway used by people, boats and other traffic is established as a 'structure' as is a road for the purposes of the regulation and if the estuary is used by pleasure boats this should be known.
The not less than 500ft from a person, vehicle or structure, pretty much excludes all of the UK from flight below 500ft.
Vast areas of the UK, in fact most parts, are free of the low level regulations and therefore they will not apply.