So, a very prompt reply to my email which says....

Gold Guest List members should not pay any cancellation fees when Avios bookings are cancelled within the correct time frame, regardless if the GGL member is travelling or not.

I have therefore made a request for £XX.00 to be refunded back to your card.

Thank you, nufnuf77 for leading me to question this - I owe you a beverage if our paths cross.