I will likely be 20 or 21 starting university due to various factors. I’m worried too about the age but I think it should be fine because quite a few people take gap years and they can easily be 20 or close to it when they start their course.
Also, there’s not a huge difference between a 20 and 18 year old in the way that they act so people won’t even bat an eye; I’m sure you’ll make loads of friends, don’t worry.