I know and can confidently say that I will always be able to understand and get my message across the radio without compromise of safety.
And that is exactly what they are looking for in this test.
You don't have to speak the Queen's English, and if you take a look through any of the tests that are around (RELTA, IAES, G-TELP, etc etc), you will notice that they are simply testing your proficiency to communicate to ATC competently in a variety of normal and non-normal situations.