People like to give themselves a pat on the back by thinking they're doing the most difficult thing ever, when in reality it isn't.
For me, I didn't revise at GCSE at all, and my grades were below par and when I started A level, I revised and didn't really see an increase in difficulty at all, only in the amount of content. With maths, my teacher at GCSE was crap and didn't teach us all the material , so when I started A level C1, C2 and S1 just felt like things we skipped over in GCSE and very basic extras. English felt the same, not much more was learnt from GCSE.
Now I'm not saying it isn't more difficult, because it is. But I was warned about this "big jump" and I started revising to accommodate that (14 hours a day) and to catch up, but that's what most of it was, catch up and if I was taught the necessary things at GCSE or actually revised, I wouldn't have to do that.
Also I find with my subject (maths); A level isn't very good at preparing for a maths degree, that might be different with the new spec although.