According to the event page, there are 15 acts before Morrissey, so you have even more to hold on for. You really have two options - queue for 24 hours in advance, then cling to the barrier like a barnacle for all 15 sets, and take a bottle with you to piss in. The alternative would be to make some friends amongst your fellow Moz-queuing maniacs on the barrier, and ask them to hold your spot during some of the lower tier bands no-one cares about, so you can cover each other for toilet breaks. But obviously, once you leave the barrier, there's no guarantee you can get back again.
Personally - and as someone who has previously queued for 24 hours + for the barrier, I'm not sure it's worth the effort at festivals. Even if you get to the barrier, he's still going to be miles away from you, and probably playing a truncated festival set.