Remember to use any online resource alongside Edexcel's specification and past papers! You can find older papers from all specs on PMT.

For convenience, here are all of Simon Baxter's notes from 2016 (taken from PMT):

FP1 notes   FP2 notes   FP3 notes   P4 notes   S2 notes   S3 notes   M2 notes   M3 notes

I couldn't find his notes for the Decision papers, but I recommend using the official textbook, my notes or SaveMyExams instead.

   Advice   

Start studying early. Further maths requires time and tons of practice. I recommend getting ahead and finishing the content as soon as possible, so you have as much time as possible for past papers. 

I've found the second year of further maths much harder than the first, particularly because of the added workload of having to study for entrance exams for university. Be ready for this step-up, especially if you have to sit the TMUA or the MAT. Start studying for your entrance exams during the first year of A-Levels.

You should have a rough plan; for example, I split my studying into 3 stages. (1) I learnt all the content very quickly, prioritising time over full understanding. (2) I then did the old exam questions split by topic on PMT. (3) Finally, I did all the new specification past papers and repeated the ones I performed poorly in.

A2 further maths relies on some of the maths content, which you may not have learnt. This will depend on how well your school sequences your classes. Make sure you know all the prerequisites; if your foundations are weak, you won't be able to progress.

Learn tricks and shortcuts to help you minimise the time you spend on each question. My notes include some of these, for example, the rule of Sarrus is one way to speed things up when dealing with matrices in FP3. There is a ton of examples, the best way to learn the most optimal methods for you is to pick out the alternative approaches in the MS.