From experience, there isn't that much complicated maths involved in economics, unless you decided to go into mathematical economics. Most of it, for me, was to do with theoretical discussions and less to do with calculating models i.e. more essays than derivations.
Standard economic courses will have modules on macro and micro, then econometrics. Macro uses GCSE level maths with simple addition and division; may have a little differentiation, but so little you won't need an A Level to understand it. Micro will involve more differentiation, but that's for things like compensating variance. Otherwise, most of it is straightforward arithmetic. Econometrics will involve a lot of hypothesis testing, and different forms of statistics.
Should you wish to study mathematical economics, it's going to take a lot of maths from the pure/core maths. As well as in depth differentian for differential and difference equations, you may need to learn matrices, trigonometry, and possibly complex numbers (some topics I think are covered in further maths). If you haven't covered matrices before, I recommend starting before going into Year 2. I have a list of recommended books for it, if interested.
Most of the complicated maths will be used to demonstrate theoretical models, and not the application of models e.g. differential and difference equations can be used to describe the movement of participants in a market towards equilibrium. Matrices will be most likely used in industrial economics where you compare in the inputs and outputs of manufacturing processes.
Although I have done a degree in management, I don't think you will be that better off with avoiding the maths in that either. When I was studying statistics in management, we covered hypothesis testing (a favourite amongst social scientists) and linear programming.
In either degrees, you will still need to cover basic statistics, much of which will be hypothesis testing in your stats module at A Level.
If in doubt, try checking the recommended texts of your modules, and ask the tutors/lecturers at your chosen uni.