Your score is dependant on all parts of the test even the parts which arent related to your branch to give you a total score. When you go for your results you will get an overview of each role which will have parts of the tests you have to pass to pass that branch, on top of that you have an overall score which for pilot has been increased from 112 to 125 this year.
Not much to say about instrument test I'm afraid it's just your ability to intepret the data from the instuments, they give you 6 options to choose from which are very similar to each other.
I'm at university at the moment not holding out much hope for the RAF they were rather blunt about my chances and chances of other people, they did strongly reccomed that if nothing happens this time round that I re apply after university and tbh the way the RAF is at this time I would much rather wait a few years have a degree and join the RAF in a better state than it is now (hopefully)