I would e-mail David and Vivienne and ask. David picked us up at the British Air business class arrivals lounge at Heathrow, and made everything so easy. In my experience, if you e-mail a question, they will promptly respond.

As to hotels, having stayed at the County Hall, and taken a tour of the Chancery Court, I think the differences are fairly pronounced. The County Hall has world class views, the Chancery Court does not. At the County Hall, if you succeed in getting the balcony upgrade, you will have one of the great hotel room views in the world. On the other hand, the service, furniture, and rooms at the Chancery Court will be, generally, superior, although the County Hall is not bad. Tough choice. It would be somewhat easier if you knew in advance you would get the balcony upgrade at the County Hall, but you won't (although you can just about be assured you will be upgraded to the view, if not the balcony.) On the other hand, if service, room, and furniture are of paramount importance to you, you would probably be happier at the Chancery Court. Either way, you probably can't go wrong.