I do not have a HHA and, therefore, don't have a F&F list. I do have a Travel Companions list. However, there's nothing stopping me booking flights using Avios for anyone else. If I say "No" to the "Is the payment card holder travelling?" question then it clears the "First Adult" fields allowing me to enter new details. I can either choose someone from my Travel Companions list or enter something completely different. As a reference point I am using Microsoft Edge as my browser.