Thank you everyone. This was useful and much appreciated.

I opted for the 797-9 although I was very lucky to get those seats.

To make a long story a little shorter, I reserved our flights via the gold helpline on the A380. I had to pay an amount in cash in addition to taxes and avois as I didn’t have sufficient points. Due to a miscalculation with taxes (I was told by the booking agent that the taxes increased £800 for no reason mid-booking) it had to be escalated to a different team and I was told that I would receive an email telling me to call back. I received an email and I called back. I paid the taxes, cash and avos and I assumed that was that. I received a confirmation email and the booking appeared as if by magic in my BA app.

So, I happened to call back a few weeks later to switch to the 787-9 the day before as 2 avoid seats had appeared, which doesn’t always happen on the SIN route.

I was told that the previous agent hadn’t in fact issued tickets to me at all, and that despite the booking appearing in my app and payment being taken etc. no final booking has been made and that if I hadn’t called to switch flights we likely would have been turned away at the airport on the day.

Anyway, I’m relieved that it was sorted out and I’m grateful that seats happened to become available the day before on the 787-9, but rather disappointed by the booking process etc via the helpline.