Waste of time
I consider these to be scam calls. Nuisance is just far too polite.
Most of the scam calls I get come from South Asia. They are made by Indians using British names.
When they can get those scumbags shut down then the ICO might not be a total waste of space.
I get relatively few UK based scam calls. There is one from 'my local energy efficiency advisor'. If they are genuinely local then at least they could fake a local phone number instead of one in Manchester.
As my home has an 'A' rating there is little I can do to improve it.