Yes, email/talk to either your UCAS supervisor if you have one, form tutor, head of year, or whoever is in charge of uni applications and ask for your application to be returned to you. You will then be able to change your options.
You can also change your course within a week or two after it has been submitted to UCAS on the website - when you look at your choices, there will be the option to withdraw your application or change your course.