The man in the background is not happy with his seat. To be fair, if he has indeed specifically asked for the best seat in the house he should expect a box of some kind. Instead he has been given a seat in the front row. Some people may believe this to be the best seat but other people prefer a more panoramic view of the stage. The man is taken all the way to the front of the stage before he realises the seat he is being offered to is not in fact the one he wanted. He probably thought he was going to be led through a side door to the Royal Box.
The usher is extremely apologetic and does in fact promise to find the man another seat. Is the Royal Box available? Could it be that a young Princess Di is attending tonight's performance? Is this in fact the Royal Variety Performance 1983 where the audience will be subjected to such acts as The Roly Polys, The Rock Steady Crew and Bonnie Langford? If it is then it is foolish for this man to think that he would be allowed to have the best seat in the house. Even if it is for charity, it's not that easy to be able to sit next to the Queen.
At the end the man believes his original seat to be the best seat in the house after all because he now has a good view of Lynne's cleavage. However he is now behind George and Lynne, which means that the seat in the front row was not his original seat after all. It now seems that after he was told he wasn't allowed in the Royal Box he was shown a selection of seats, the second of which was the front row, to which he said "But I paid for the best seat in the house" to all of them. The first seat he was shown is the one behind George and Lynne and now they have sat down he realises that this initial option was in fact the best. It's now clear that staring at Lynne's chest counts as far better entertainment than Wayne Sleep or the British Amateur Gymanastics Team.