GrahamK,
Your comment regarding domestic travel is valid but it does not invalidate my own point. The railways have made inroads into the Manchester-London market. However, the cutbacks in BA MAN-LHR Shuttles were evident well before the West Coast Main Line upgrade was completed. Returning to my point regarding Skipness' post, EK/EY/QR/SQ have established themselves as the carriers of choice on the 'Kangaroo Route' from the North. I'm sure that QANTAS themselves are well aware that their LHR transfers are significantly disadvantaged against these more reliable and superior* products.
* 'Superior' here refers not to onboard cabin service, but to the transfer experience at LHR and the notorious unreliability of the frequently cancelled MAN-LHR Shuttles.
SHED.