I'm not entirely sure but an educated guess would suggest "Psychology: The Science of Mind and Behaviour" and "Themes, Issues and Debates in Psychology", both by Richard Gross. However as you probably already know most of these textbooks cost quite a bit of money.
Extensive reading lists are provided during the first week of lectures and tutorials/seminars/labs begin in the third week of teaching which gives you a small amount of time to buy books. I don't think undergraduates recieve reading lists before the start of the first teaching week (14th Sept this year) as far as i know.
But you may be given quite a long reading list for each week of teaching, so you should think about just buying the highlighted key texts and your extra readings can be checked out or studied in the library. I only say this because depending on the subject some reading lists can include well over 50+ books and it's just not feasible to buy them all. For Psychology however i can't imagine the list to be quite that long.