Generally speaking it's the same pattern of questions every year with the odd twist. I would really recommend doing the Solomon past papers over the exam board ones as they're made to the hardest level which could be set, meaning you can be prepared for the worst.
S1 isn't too bad it's just a bit of a memory game rather than a maths exam. C3 and 4 are very different to core 3 and 4 though. The vast of them is just integrating and differentiating more and more complicated things, but it gets really hard really fast imo.