My team play with a 3-5-2 but if I wanted to switch to having 4 up front (lets say for corners) or 5-3-2 (for last 10 mins when winning) how can I set that up so I don't need to go into the formation screen and mess around with it that way?
You can assign 2 additional formations to a Strategy button. You need to set them up in the formations menu (Strategy Plan A and B) and then assign them to a strategy button.
Firstly you can go into Data management and copy the current "normal" formation onto "Strategy Plan A" and "Strategy Plan B" to have a basis for modification (or you can choose a formation like you would normally do).
Then go to "Team" and Strategy Plan A and B. Once you press either you can edit them as you wish. Once the formation is to your liking, to into "Change Gameplane" and assign to a prefered button "Strategy Plan A" or "B". Then in game you hold L2 and press the button you chose to activate the strategy.