As I can't see all with shifts, Olivia and 1975 would be perfect. Seeing Sam in Manchester but would need to really love the new album for it to be better than last time
If there are a couple of acts you want to see at opposite ends of the site, and less than an hour between set times, pick one and don't worry about the other. One of my rookie errors in 2007 was trying to traverse the site too quickly. On the flipside, start walking to your must-see act way before you think you need to, so you can lap up the atmosphere and take the inevitable detours along the way.