There was an injured BBC player to the right of where the winning goal kick was taken. Those with access to the footage may be able to see if he was taken off on the eastern side. If so then it was 15 v 15.
If there were 16 players on the park, there are two possible laws of the game that could come into play here, the 16 player rule (law 3.2c) and the rule about the player only able to enter the field with the permission of the referee - law 3.11(c).
Law 3.2c "at any time before or during a match a team may make an objection to the referee about the number of players in their opponents’ team. As soon as the referee knows that a team has too many players, the referee must order the captain of that team to reduce the number appropriately. The score at the time of the objection remains unaltered.
Sanction: Penalty at the place where the match would restart".
Churchie didn't appear to make an objection to the referee at any stage during the match about numbers. The coaching staff on the sideline may have said something to the TJ, who is not the referee so technically they can't win on that one. If you don't agree with that interpretation and we take it to the next step, the first thing that the referee would try to do is count the players - almost impossible once the pitch had been invaded by students. Even if you went to the next step and awarded the penalty, the penalty would either have to be at the centre of the half way line or where the BBC player kicked the ball out to end the game, which was 40 metres out and about 5 metres in, neither being real penalty kickable places. Sorry but I can't get past step one here - nobody objected to the referee, and who is a "team" anyway? The players or the coaching staff on the sideline? so 3.2 doesn't apply IMO.
Law 3.11(c) bears more scrutiny though
"If a player rejoins or a replacement/substitute joins the match without the referee’s permission, and the referee believes the player did so to help that player’s team or obstruct the opposing team, the referee penalises the player for misconduct.
Sanction: A penalty kick is awarded at the place where play would restart".
I think that the player concerned definitely didn't have the permission of the referee to enter the field - after all he didn't know that the incident occurred. Because the referee didn't know that the incident had occurred, he wouldn't have an opinion about whether it was done deliberately to help his team. No belief on the part of the referee therefore no penalty kick by my interpretation of that rule.
Sorry very technical, but I don't think Churchie have a case. I also concur with the opinion of vegas that the kickoff took place after full time. I also concur with the view that it would have not been the way to end a great game of rugby. If the field had been cleared and we had a penalty (can a ref restart a game after full time has been blown?), and Churchie got it, then BBC would be putting some of the arguments forward that I have put above.
Basically get over it folks! It is only schoolboy rugby.