Don't do IT at A level, these others are right in saying its a dying failed and utterly useless. Although I can't speak on the business/economics side of things as I have never done it if they are saying the some of the top uni's don't count business as an A level (like most uni's with stuff like critical thinking or whatever its called) then you would be making a mistake by taking it.
You are also massively overestimating how hard A levels are and how much work you have, 3 A levels even if you took maths, further maths and physics allow you to have a manageable workload. The problem of workload and it being hard arises most of the time when people take 4 hard A levels like maths, further maths, physics and chemistry for example.
Computer science is not a hard A level, some prior knowledge is useful though but not necessarily needed but it will make starting it a little easier. It doesn't require too much work either. Maths isn't that hard, if you're **** at maths then yeah it will be but the work isn't much and its perfectly possible.
You are basically currently considering 2 useless and easy A levels (IT just has lots of work but it isn't hard) and wanting to take an even easier 3rd one for fun and quite frankly if you are worried about the workload and difficulty of them then I don't think A levels are for you.
I would recommend:
- Maths - an incredibly useful A level to have
- Computer Science - much more relevant and beneficial for you than IT, I have never seen any uni course ask for IT but loads for computer science and it will allow you to go into more areas
- Economics - apparently like business but better
- Any 4th one you want, if you can pick one you will enjoy and might be relevant then great but doesn't need to be, it does give you leeway to drop a subject though if needed which is why it will be better if it's slightly more relevant to what you want to do. I cannot recommend taking four enough even if you don't finish with four as you dropped one
A levels aren't meant to be easy but they also aren't impossible either
Can I ask what grades you are currently working at and projected to get in your GCSEs?