Thanks for the help.
I can see the point about the going through the same city twice, I guess I was thinking about it differently, as Marseille is the only European stopover we want, just transitting LGW to get there. Would be happy to go MRS-HKG by not going back through LGW, but there really was no option
You mention a route map for this fare - have you got an online link for that? We haven't seen one. Actually, it was a hard fare to find all the information about at all...
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">On the third hand ( ) my TA has managed to get BA to be pretty flexible on this type of ticket in the past.</font>
Thanks for the encouragement

We've pushed on with it to see if we can make it work for this itinerary.