IanS: When you're out in BC in May you should consider posting an invitation for a BC No. 4T owner to meet up with you and your father along with his rifle and kit. That would be an exceptional opportunity for a collector to meet an individual like your father and show his "T" to one of the original users. As far as owning a "T", there's no questioning the appeal. However, they're not really any more entertaining for casual shooting than any other No. 4 (I get my biggest blast out of shooting my No. 5 carbine). Given the difficult task of finding a "T" that's both affordable and absolutely genuine, maybe you should consider looking for an excellent example of it's main progenitor- a typical BSA No. 4. Your father probably trained with one like it (or a No.1 or maybe a No. 3).
Ridolpho