Variational calculus is covered in most textbooks on mathematical methods in physics (including mine), but I suspect you are not after an entire textbook. Does your module not specify some literature or recommended reading?
No my module leader says he is uploading his own sets of notes for each section but I would like to have a second resource to see things explained in a different way.
It might help to see if you can find a resource that is usable for all modules. In particular if you are after a textbook. If you are just going module to module I would try to find lecture notes online.
That is quite a lot of maths and it is difficult to jam it all into one book. If you really start from the beginning, like introductory calculus, linear algebra, and ordinary differential equations, you could be looking at something like Riley, Hobson, Bence. If you are passed that level, I would (obviously biased) suggest my book or Arfken or Boas depending on your preference.