Oz allows training from any airfield, airstrip or paddock that meets the a/c's performance requirements, licenced or not. Oz also publishes an advisory publication that gives recommended dimensions including approach & departure gradients for unlicenced airstrips.
As far as I've been able to determine, the safety rate for training in the UK is no better than in Oz and, I believe, comparable to the US which has far worse weather & terrain than the UK. That begs the question: What justification is there for the UK additional requirements?