A levels good enough for chemical engineering

I have taken Maths, Chemistry and D.T (Product Design). I am looking to go to top uni's in chemical engineering (Queens mary, UCL, Brunel). I am not looking to go to very very highly regarded unis such as cambridge and oxford. I just want to know if these a level choices are good to apply for these courses while achieveing there desired entry requirements (AAA/AAB).I can replace dt for physics which I have heard is better for Engineering in general, but to do that I have to get a 7gpa in my GCSE results. I achieved just one mark under a 7 gpa (as I was one mark of an 8 in chemistry which would have increased my gpa to 7. Now I have applied for a remark but haven't payed for it and I have heard it takes up to 20 days for it. The problem is that the deadline to change DT to physics is 20th September and if it doesn't come back by then, then I cant change DT to physics. Any advice on my situation and how long a remark takes and the chances that my chem grade will go from a 7 to an 8