Trying to find this movie I watched once online…. Honestly don’t think I would consider it horror really…. But not sure what other category it would be under… maybe thriller?

During the pandemic I was on a streaming marathon of movies via Amazon, vudu, Netflix, etc. I unfortunately watched so many I lost track of some and am currently looking for a certain movie. I believe it was a foreign movie taking place in the UK or AU (I just remember they all spoke English but had accents) It was a bunch of teenagers in a psych hospital (I believe) they kind of had the run of the place and at one point found a staff member's (who was Mia) keys and took his car down into town. While there 3 of the guys went into a convenience store to get alcohol and also found a gun, the girls stayed outside and upon hearing a noise a girl goes down into a subway or market area downstairs and is attacked by a zombie? Or infected crazy person. Back in the store they are attacked by someone as well and one of the boys is killed. They regroup and make a plan to escape. One of the boys fathers owns a boat and they make a plan to head for that... That's about all I remember (ad) does anyone know the name of this movie?
thanks in advance!