Tom, assuming you're staying in the same hotel all weekend, you'll need to let Gerry know, so he can book you the extra night (it's fri/sat/sun/mon inc in price). Unless you have already.
Dom, as I understand from Gerry's earlier post, he's sending out a 'pack' which will allow us to book these extra days:
"We'll be sending out an info pack in the next weeks. This will have a rooming request form so we can match up 'room mates' and dates. Extra days shouldn't be a problem - there's more chance of getting a better rate with the group booking but it's up to you. (may get a bit confusing for the hotel though). Thanks Gerry"