Samsung have a discounted site which you can access through perks at work - look into this and see if you can make an account. Students also have access to the reduced prices and there's various other ways of accessing the 'discounted' samsung store but if you can access the website via one of these, the 256gb s24 ultra is (or was) £999. Trade in bought it down to £899 which was basically trading in ANY broken handset and the cashback brings it to £699 - with the free watch6.
The discount site however doesn't accept voucher codes. It was my birthday last month and I used the 15% code that samsung emailed me, with the 5% code for using the app for the first time with tons of others codes at the time that were all stacking up to bring the s24 ultra down from £1249 (main site) to £609. This was before the cashback or watch6 offer but I was happy to pay £609 for it.