hi i'm also applying for chem eng(cambridge(probs rejection),imperial(A*A*A*),UCL(AAA),Nottingham(AAA), Shefiield(AAA)). I'm probs gonna put imperial as firm and ucl as insurance even though i've spoken to people currently doing chem eng at UCL (2nd years) and they all said not to come. In terms of imperial interview, try and find something in chem eng that you're passionate about, for me it was the research side. They'll give you an academic question on maths and chem. Hard maths q+easy chem q or super easy maths q+super hard chem q. I got the easy maths and hard chem q but then again difficulty is subjective. It's all based on A-level/AS level content, I didn't get any personal statement q's but apparently one person did. Surprisingly i messed up the math's q and did well in the chem so i got the typical offer of 3A*'S (doing three alevel's: maths,chem and physics + AS further maths). Most likely you'll get 2A*2A offer. (unless you do really bad in your interview that they're not sure then they may increase it).