My personal take on this is to book everything that is “speculative” as a BAH. I have a FTV to the value of £500 which was the result of a Holiday I had to cancel. Seeing as that is now tied up with BA in some way shape or form, I have no issue using it towards another deposit - irrespective of it maybe having less than 10% chances of going ahead. There have been some great prices of late so if it’s something I think could happen I book. When I know it won’t happen I cancel, get my voucher and start again.

I would be very hesitant to be starting a new booking with “new” money though.