Stephen64 Couldrey

Hi I am a UK resident. I have a "Retirement Savings Plan"/ 401K from a former employer, it is in US$ and located in the US. I was working overseas as an expatriate when I got the 401K i.e. I have never been a US citizen or worked in the US. I want to make a withdrawal from the 401K and I was told today by the plan administrators that the Tax Treaty between the UK and the US changed in 2024 to the effect that because I have a UK address any withdrawal is subject to 30% US withholding tax. My question is, did the UK tax treaty with the US change in 2024 as it relates to 401k withdrawals? Second question, if the US deducts 30% from any withdrawal, am I also liable for UK tax? thank you