I would commend the OP for a very balanced and fair review of the BA product offer. It's a shame that perceptions, on here and in the press, put people off what is a reasonable product.
Not sure about T5. Without lounge access it would be a pain, but I wouldn't get there any earlier than necessary. My judgement of JNB, IST, CDG etc is similarly coloured by having lounge access. I would say Exclusive Books at JNB is light years ahead of anything at LHR.