
Hello Philippa Rollo,
Welcome to Microsoft Q&A
Does your account have alternate way to sign in? Such as Authenticator App, SMS text message, Alternate Email Address. If yes, then you could try use such method to sign in.
Refer to this site for info on alternate sign in method:
Use the account that you still have access to get in contact with Microsoft Support Chat for further assistance:
- Open a website link - Contact - Microsoft Support
- In the box below "We're here to help", type Microsoft 365, click "Get Help", and then click "Contact Support" below.
- In this section, you will need to sign in to your Microsoft account.
- Select "Microsoft 365 and Office" under Products & Services, select "Technical Support" as the category, and click to confirm
- You can select " Chat with a support agent in your web browser " to access the chat window. Contact - Microsoft Support.
Best Regards,
Xavier-Microsoft Q&A Support Specialist.