You still have to be 500' from the dam at the end of the reservoir though...
But let's not forget;
- many AOC operators have permanent exemptions reducing the 500' to 200' for the purpose of filming & photography with some obtaining permissions for even less separation than that.
- HEMS & Police have special permissions in force (no rule 5 when it's a 'HEMS' flight).
- power line patrols have exemptions to be very low;
- both fixed wing and helicopters carry out pipeline patrols circa 500ft AGL and above;
So yes, there are man civilian aircraft operating throughout the UK low level EVERY day.
0-500ft AGL is not just for military aircraft.
Flying low isn't dangerous - pilot attitude is dangerous!