-Thanks for posting the fantastic photos. You weren't exaggerating about condition. When you find something this pristine there are 3 scenarios...Thanks. There's some discussion whether its "too nice"
1.) Unissued - Harder to swallow with a '41 date. Cannot imagine any SMLE assembled in '41 didn't make it into the field, not with the Japanese knocking on your doors and Australia desperate for small arms.
2.) FTR (Factory Through Repair) - Much more likely with many wartime SMLEs getting refurbished post war then put into reserve storage when the SLR was adopted in the late 50's.
3.) Assembled from NOS or refurbed components post war. JJ got a massive pile of spares along with rifles from reserve stores. I've got one of the No2 MKIV .22 trainers that was built by JJ using a spare barrelled action. It got a unique JJ stamped SN so easy to ID. All of the JJ assembled No1s using NOS spare actions have a unique JJ assigned "A" suffix, unlike yours which has a correct B series prefix. So not a NOS action. Don't think JJ refinished any actions, though I have no proof of this, just my observations over time.
-At this point I'm leaning towards you having a factory refinished barrelled action that was installed into a NOS stock set as I don't see any FTR refurb marks and it has an original SN. It's also possible that it has the original metal finish though I'd be surprised that if that was the case. Just too pristine.
-In cases like this my go-to component is the nose cap. If my guess is correct the nose cap will not have a matching SN or be blank (another NOS part). If the action and stock set left the factory mated the nose cap will have a matching SN.
That said, I defer to 303 Enfield as his knowledge in all things Enfield is superior to mine. Love to hear what he thinks.