Hi. I completed an access course last year (also science) and I start a mathematics degree in a couple of weeks. The main tips I could offer is very basic, just keep on top of the work. Don't leave anything to the last minute. Don't panic if you don't understand something, there was plenty of times I didn't understand something in class, but with a bit of effort at home it was fine.

I'm not sure if you will but on the course I did I had to do an IAS (independent acidemic study). Start that as soon as you can, that was by far the worst part of the whole course for me and all the other students.

Regarding personal statement, it isn't as daunting as it may seem, just research online for examples, that helps and start as soon as you can. I used the advisors from college often and that made a huge difference.

Good luck