DSC 1 may not be mandatory, but it’s becoming essential.
The UK is pretty much alone in Europe in not having a recognised National hunting certificate and qualification or a deer hunting licence.
I’ve had to provide details of my qualifications to my hosts in a few foreign countries, if you can’t do that then you have to come up with something else. Even if you never hunt abroad it’s useful to have because it demonstrates that you have achieved a basic level of knowledge of the subject.
My advice would be to get it, its much like moving to lead free ammunition now, before it becomes mandatory, you’ve future proofed yourself against what’s likely to happen sooner or later.