Please refrain from using caps lock (capital letters).
Well, I have also done only math in IGs and I AM currently taking M1.
I am not sure about what P1 is but as I did AS math (edexcel) already and am doing M1, I dont think you need any additional thing other than IG math to understand it. Maybe a bit of physics but you dont need anything like additional math or something in IGs.
By the way, can I know which country are you in currently? and are you taking edexcel or a different board?