YouFirst is just a telephone number - your call is picked up (I don't think I've ever waited more than 60 seconds) by the GGL contact team in the UK during office hours and in India post 8pm. They are fully trained booking agents and not a concierge service.

I use them for every element of an F booking that I can't do online. They are invaluable during disruption for the speed with which you can get through, and for the luxury of making less urgent quote enquires and flight changes via email. The agents are some of the most knowledgable in my experience, and expertly construct my awkward fares from the ITA matrix, once even suggesting a cheaper alternative I had not spotted. Ordering menus and booking cabanas is definitely not using them to their potential.

I have almost always found them to be charming - I can only recall one grumpy agent in my years of using them. I find the India call team particularly excellent and flexible.