Might sound like an odd question, but to take advantage of the current BA Miles promotion (only applies to return bookings, not single legs), I want to make a booking to the USA but I already have a return leg BA Miles redemption booking in J, so I was planning doing the following:

Book a flight out to USA on the date I want in F, with a return date sometime in the future (but after my existing redemption booking) in WT

I would then fly out in F, return a week later on my existing booking in J, and just not bother with the WT booking.

Would there be any problems with this? Other than losing the BA Miles for the WT leg and the extra tax (about £72pp), would this be allowable?

You might ask why I am doing it this way. Well, it's because for my existing return date, there are zero redemption seats available in any class, which I am surprised about, and I have to come back that day, so I need to keep that leg. So I would be cancelling the original outbound redemption booking in J (100,000 miles) and rebooking as above in F (for the same 100,000 miles & the slightly extra tax).

The end result is, no extra miles spent, but an "upgrade" to F for about £72 each for myself and my wife.

If I have got this horribly wrong, could someone better qualified please let me know before I cancel my outbound flight.

Many thanks,
Kevin.