I can’t say I’m surprised by the low transfer loads on Little Red flights, for two reasons that have affected me personally.
Firstly, anyone who booked long haul flights out of Heathrow many months ago (in my case an Air New Zealand flight next month) with a domestic transfer will have been put on a BA flight. When I made the booking Little Red was not an option, and I’m not going to now pay to change my domestic connections from BA to VS. I’m sure there are many other passengers who also made reservations many months in advance, prior to VS becoming an option.
Secondly, while BMI had connections to all Star Alliance members, as well as several other carriers at Heathrow, VS has comparatively few code share partners just now. None of United, US airways, or Air Canada have code share partnerships with VS via LHR (as I discovered at the weekend while trying to book a flight to America in December).
I’m sure connecting passenger numbers will increase on Little Red flights, but more codeshare agreements with Star Alliance or Sky Team carriers will be required.