I have poor command of English Language but still managed to get 7.5 for the essay part..which might calm you down a little..i think the content is more important than anything else..though grammar might be taken into account too. The first section is something that you can't really revise for..it's all about critical reasoning, passages, comprehension and those stuff. The second section tests you on the sciences..and the application of them..i scored 6.2 in that section, which i think is considered quite a decent score..so i think it should be fine with you as long as you know those things in GCSE..such as background count of radioactivity.This section involves a tiny bit of critical reasoning too. I was given a table and asked to calculate things from it..it's not a normal kind of table and involved lots of formula and the units are extremely confusing..so were the subjects in the table but once you've grabbed what it's trying to show you'll most probably get the associated questions right.