I did the foundation this year ! (you finish on april 30th)
I found that the unis, tho linked, didn't rly feel like it and we never rly mixed??
You can go to the Leeds arts uni societies things, but u don't rly get told about it on foundation. You do have free reign of all the unis social things, you can go to both university sites too. Foundation students just tend not to go, and stick with just foundation social things.
It was rly amazing, you won't regret it. srs first term is a bit confusing bc everyone new, but it gets a lot better.
I wanted to join some societies, but was fine n happy without! You meet a lot of people, and change up classes/seats a few times.