What I do is this.

gla -Lhr/Lgw and book CE but use my avios to get down to the Economy fare so it doesn't cost my company any more. Once a month gets me 960 points and 24k avios.

on long haul I fly WT+ and get a min of 18k miles/trip. So in your case that would be 54K to 72k. Since some of your trips will be in J let's call it a yearly total of 100k avios. So each month you have 8k avios to bring the cost of the CE flight to the economy price. Okay, it may take a year but going only BA will have you at silver in about 4 months so gettin lounge access. Then gold at the end of the year.


factor in a couple of crazy ex EU TP runs in J and you will be fine.