Do not go out and buy tons of textbooks!
You will have an enormous, well stocked library, most stuff is accessed online - and for most books on any reading list, you will usually only look at odd chapters, or at best use them for one topic. AND, if you do need to buy a general text for any 1st year course, wait until you get there and you can buy a second hand copy of one of last year's students.
For this reason, discourage any well-meaning relative about giving you Waterstones etc gift cards as a Going to Uni present - they will still be in your wallet at the end of your degree. Ask for Sainsburys, Boots, or Uber giftcards - these will actually be some use.