I would recommend getting them 2nd hand.
Also all the extras that come with the core texts aren't really needed anyway.
You don't need the latest editions either, some are almost identical.
All your subjects this year (except stats) will have lecture notes which have a good outline of what you need to know already.
Your lecturers will write the exams based on the lecture notes and not the textbook.
The textbooks are good if you have no background in science and need extra detail that some lecturers do not give.
I found myself consulting the lecture notes more often than the textbooks, the two core texts were quite wordy and I could never bring myself to read them and managed to pass every subject.
Anyway, good luck!