Originally Posted by Lefly

I have no idea about the pricing you have in mind, but If you really, really have to buy a 4th ticket, wouldn't be better if it could be allocated to a travelling person... a sister's friend maybe? At least it will not be wasted... I have no direct info regarding what could happen if the travel companion doesn't show up at check-in for these "companion" fares, but I don't rule out the chance of troubles.

About the rest, you can lower the price with avios, even if it's not the best use of them.

Out of curiosity, why do you worry about the flights for the 3 of you not having the same reference?

P.S.
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