Looking at lecture notes now is not a good idea. I looked at a few after I had done all of my exams of one of the courses I'm actually doing now, and it was completely incomprehensible and filled me with dread.
As mentioned before, "a concise introduction to pure mathematics" is a very nice book to get, it follows on from A levels smoothly and explains things in easy to understand ways. It has a few exercises at the end of each section just to reinforce some ideas, really good for doing a bit of over the summer.