[QUOTE=AJA_;36786685
Also I assume you are phoning the GGL line to book this which may contravene this clause
22. Reward Flight bookings made with Companion Vouchers can only be redeemed online through the British Airways Executive Club Avios Reward Flight booking page and British Airways Executive Club app or through British Airways Contact Centres, and Companion Vouchers must be applied at the time of booking through your British Airways Executive Club account.
Unless your son-in-law is eligible to phone the GGL line in his own right I don't see how you phoning it will help.

As for a way around this are you and your daughter and son-in-law in a HHA? That way you would contribute Avios in proportion to the HHA towards the reservation ie pay the majority of the Avios. You may still have a restriction on using the GUF2 as you state that to use it you have to use your Avios and your status releases space. That said I don't think you are able to use your GUF2 for other travellers if you are not on the reservation yourself? So that would also be in contravention of the GUF2 terms and scupper your plan.[/QUOTE]

As I said in my original post, I had done exactly this 9 months ago. The rules on using GUFs and space releases are clear - providing I pay for the booking (whether with cash or avios or a mix) I can use them whether or not I'm travelling,

What has changed from 9 months ago is being denied the ability to use one of the passengers' companion voucher.

The question I asked was purely about whether or not, given the wording of the clause of the Ts&Cs quoted, the companion voucher holder is indeed the only person that can pay for flights being acquired using said voucher.

To me it's fairly clear, but I wondered whether someone with more legal knowledge than me might have a more nuanced opinion.