Pumpkin - it’s been a few years since I left, but I distinctly recall being strongly advised to ensure that any funds arrived in my UK bank well before I arrived in order to avoid any potential tax implications. Fortunately this advice was largely academic for me because I was moving my funds and myself to another country, but it may be something you should look into to avoid any nasty surprises. Maybe some other leavers could comment further. I believe similar cautions apply to returning to the US. A secondary consideration involves the possible implications of arriving in any country these days with large amounts of cash due to Money Laundering and Financing of Terrorism rules.
Best of luck.