Hey there orangecake
If you're thinking of applying to study medicine, which I presume you are, you
NEED to do chemistry.
Sorry I can't help you out about whether there are any evening classes taught around Birmingham, but it's pretty big - I'd imagine there are a few places. Maybe have a search for some adult learning places (I spos you're kinda doing that by posting here, but just saying)
So, if you take up a chemistry a level evening class, are you thinking of dropping one of your current as levels? Not saying that you're not capable, but, as I'm sure you've found out, chemistry is alot of work (I'm doing AS at the moment - fun, but loads of work!) Dropping one might be good for giving you extra time to get your chem grade up.
On the otherhand, if you think you're going to get AAAA in the subjects you're doing at the moment, do you really want to drop an A grade subject for something you think you won't do as well in?
Well, like I said - if you want to do medicine you need to do chemistry. You're getting fab grades in everything else! I'm sure you could do really well im chem too, just might take a bit of extra practice.
Best of luck
Emma x