I would like to reply. I do not know if I have had a disappointing performance in gcse geography but what I meant is that I found the exam to be very unpleasant and not what I was expecting. That has little to do with my preparation as my teacher was telling us to focus on our case studies for volcanoes and earthquakes which weren't even in the paper. I would also like to add that I do work very hard on my current work.
As to developing problem solving skills, I do practise BMO problems and will be entering this year. I also enjoy competitive programming. However, I want to practise STEP. I am not saying do it full time or even a lot but just a bit every week to develop my skills over the coming years. I apologise for not specifying this in the original post. I also have no school mathematics to focus on at present as I did my GCSE mathematics 3 years ago and got an A which was disappointing at the time but there were also extenuating circumstances at that period of my exam which I would rather not disclose.
Again, I would like to emphasise that I am not intending to let it get in the way of other studies but just do some every week or so to slowly develop and I feel some assumptions were made here, greatly my own fault for not being more specific. With these new parameters, can anyone recommend a way for me to prepare for STEP that I can gradually practise over the upcoming period of time.