With those predicted grades I'm afraid to say you do not stand a chance. You will probably be rejected right off the bat and they will likely not even bother interviewing you.
Last year most applicants who applied to Imperial for Chemical Engineering had been mentioned as runner ups or honourable mentions or better in the IMO and Putnam competitions and had multiple publications surrounding Chemical Engineering.
At the very minimum they usually require you to have taken at least 5 A levels in the span of 1 year and expect you to have had an internship at Jane Street, Google or some related companies.
Yep... Things are looking pretty bleak for you right now to say the least pal.