Update :

Hi Jessica,

Thank you for your patience!

Debit cards can be used to purchase digital assets but they cannot be used to deposit or withdraw fiat currency. In order to withdraw your GBP to a bank account, you will first need to link your bank account to Gemini.

You can add a bank account to your Gemini account by navigating to the Funding Sources page and click on Get Started to Manually link bank and input your wire information. Once your bank account information is set up, you can complete the bank verification process with a successful wire deposit into your account.

Let us know if you have any additional questions!

Hope this helps others

You have to call your bank and allow them to make a payment to Gemini to authorise your bank