It's definitely a lot more challenging. But practice makes perfect. Also need to understand concepts in and out... mark schemes are very specific and lack leniency, but actual marking by examiners, I'm not so sure about. The trick is to understand how the paper thinks, if that makes any sense. Lately that's been a little difficult as the format of papers change a lot. REMEMBER it's not just studying. It's understanding!
(Got A*s for maths and physics at IGCSE and expecting an A for As physics. If you stay motivated you can do it. Cheers!)