Thanks again, Bob. The pointwork in the photos via the link would be what I’d be aiming at. Re bogies on locos, yes, I agree. The push-along T9 still has virtually all the bogie side-swing which Hornby designed into it. The tighter P4 clearances keep the yawing down, and I think a weighted tender resting on the drawbar might also help to prevent front-end wobble. However, it is difficult to place on the track and one can feel the resistance being encountered against the wheels, but not so much that force is needed.
All in all, most interesting, and I’m grateful for your comments and links. I also take your point re the wider back-to-back, so the George Watts B-to-B gauge will come in useful as it is adjustable for all the 4mm scale gauges; I think the only thing to do is try to build a point to EM-SF and experiment.