If you are really confident you can achieve a higher grade than predicted, talk to your subject teacher. I asked for my predicted A in Biology to be raised to A*. I explained that I work best under pressure (which is true), I exceeded predicted grades at GCSE and in my EPQ. My teacher said he would set me a test and if I achieved A* he would raise it.
Up to then my test results had been 50/50 A/A* so he admitted i was on the cusp.
I got the A* in the test and in my actual A'Level exam. (I also got the offer I wanted from Durham).
Definitely worth asking though sounds like you would get a contextual offer anyway.