IB HL Further Maths resources

Hi all,
I am doing HL Maths at IB and heard about HL FM. I thought it might be interesting and fun to do it on my own purely for broadening my mathematical horizons (i.e. not taking it as a subject). I know that it is very, very difficult and that there is enough work within the IB to be getting on with but as I know from experience efforts like these can boost understanding. My question is, are there any resources out there that would enable me to dig into the subject? Is there a textbook or a study guide? Are there any downloadable past papers whatsoever? Thank you for your answers and opinions.