I have now had some time to work out how my purchasing will change.
I live outside the South East and have been silver for five years. I have been using BA to fly NCL to LHR for London trips, to fly to LHR to connect to European cities and then one long haul flight in F a year. I also use EZY to fly domestic elsewhere and TUI to fly on some hols.
Without loyalty, I will take more direct short haul flights with other airlines - am thinking Air France and KLM in particular. If I am going to London only, I will consider the cost of the train vs flying, taking into account that the train does get me into central London. I like the short haul business product if I can get it at value because the seat blocking is good for me.
As for long haul, its just going to be an open competition based on price for premium cabins/destination. There is some convenience in terms of T5 transfers from domestic to long haul, but it isn't the only factor.
Overall, unless I decide to take a BA holiday on a long haul route (which I wont rule out, but it would not be frequently) then my overall spend will decrease.