I am an instructor at Oxford and in the 4 years that I have been there I have seen a very wide variety of students pass through these hallowed portals. Some have extremely fine degrees and I wouldn't trust them to post a letter. Other have just 5 GCSEs, but so much practical intelligence that I just know that they would come to a broad pragmatic solution to any problem which would be safe and sensible.
It's the second sort that I would choose to be airline pilots. There is no doubt that you are required to be intelligent - but it's not an intellectual kind of intelligence. It's a practical intelligence. Can you sort out a circuit diagram? There is no doubt that you need to be numerate - but only at about GCSE level. Are you good at rapid mental arithmetic? Can you re-arrange elementary equations quickly? No-one is going to ask you for calculus or hyperbolic functions as an airline pilot. But you are going to be required to work out how long your fuel will last -and come up with the answer very quickly.
Apart from this, the most importance factor is motivation. If you think you'd just die if you didn't fly, then you must fly. If you don't come into that category and there are lots of other things that you think that you might enjoy, then I suggest that you go and do one of those instead.
The airlines understand all this. Recruiting managers and training captains have been around and seen all this.