There are hundreds (?) of subtle differences. Get ready for another 5 pages of examples..................
I'll start. The UKchange levers are retained internally with a small hard-to-get-out split pin while Aust ones don't have the hole. Anyone else.
It is worth remembering that in places like Malaya during the 60's, with pooled/pro-rata Ordnance stores Australian, UK/Gurkha, NZ and Malayan attached units could have BSA/Enfield and Lithgow rifles. So it was important that while spare parts might be slightly different, they fully interchanged and functioned properly. I can only think of one example where this caused a real problem