I've never understood the UKs restrictive policies. In Oz you're allowed to conduct any level of training from any type of airfield as long as the field is suitable for use by that aircraft. Oz has an advisory publication that give recommended dimensions incl. fly over areas, surface & approach/departure slopes etc. Of course the field must be long enough IAW the aircraft's performance charts.
Historically, these aircraft landing area (ALA) specs. were in the ANOs/AIP, with a slightly more restrictive version for training (called a training ALA). Some differences included shallower obstacle clear approach/departure gradients. The training ALA additional restrictions were dropped around ~10 or 15 years ago.
As far as I can find there is no difference in accident or injury rate between training at licenced aerodromes (which may or may not have a fire service. It's not required, anyway), ALAs or the defunct Training ALAs.
So, why does the UK bother?