I think it doesn't really matter. A foundation year is year 0, so even if a uni has a fabulous foundation year but the course you are progressing to is rubbish, you kinda lose.
Ask yourself, which is the best among those unis in this engineering discipline, that way it's a win-win.
I don't know about being able to switch to chemical, but I think you can because most unis give you the foundation year to also decide which disciple you would like to progress into. But make sure you tailor your foundation course towards chemical by choosing the right modules