IIRC when booking an UUA flight on BA.com sometimes the booking class for the ticket being upgraded defaults to a flexible/semi-flexible ticket so can come out at a fairly expensive price. I've done some dummy bookings recently for UUA ET to CE for a trip I'm making early next year and the price was significantly more than just booking CE as a cash booking.
Those with more expertise will be along to point you in the right direction, but (again IIRC!) it's cheaper to book the cheapest WTP ticket on BA.com and then phone to process the upgrade, availability permitting of course. I'm certain I've read on here before that all WTP ticket classes can be UUA to CW. I had to do this last year for a CW booking, BOS > LHR. There was availability in F but when going through the UUA process on BA.com the price was eye watering.
Last edited by GlasgowBlue; Sep 29, 2019 at 9:41 am