There was a case where a family chased a burglar for a mile, held him down and ran over him. That wasnt deemed reasonable force. And I suppose if I had a burglar under control, then preceded to pick up a lamp and bash his brains in and almost kill him, then that wouldnt be reasonable either.
The cases where UK householders have been prosecuted has actually been tiny. Tiny. Despite the belief on here.
No viable self defense option exists for me but ready access to a gun. In the U.K. I would have no options at all.
As for having a burglar "under control", no way, he will go back out of my door feet first and belly up.