Many Unis won't accept Functional Skills - because it really is a sign of very basic achievement in English, and they want higher than that as an indication of your ability to cope with any Uni level course.
You still have time to retake English properly and get a better overall grade. ASk your school about this and if you decide to do it, you can just list GCSE English as a 'pending' retake on your application. Offers would then be conditional on you passing it with the required grade.
Its worth doing this anyway - future job applications could also depend on this basic requirement, regardless of your degree.