Firstly, barely more than a week since emailing and less than a month since submitting an automated form enquiry is really not unrealistic. The form maybe is getting on a bit although those things are never exactly reliable to start with. Basically no chance you're going to get an email response within just a week. If you don't hear back within a month by email then maybe be a little concerned.
Anyway, managing your expectations about university administration response times aside, do you actually hold an offer from them already? If so then you don't really have too much to worry about as it's not like it will go away. If not then you would have needed to contact UCAS within 2 weeks of submitting an application to change it, not the uni.