You can try the following:
[Lodger full name]
Date: [Today’s date]
Reference: [Property address]
Dear [Lodger name],
You currently have an excluded lodger agreement with me because you share accommodation with me in my home.
It is with regret that I wish to terminate the lodger agreement.
I therefore hereby give you notice that I require you to vacate the room, premises, facilities you share with me and my home on or before [insert date with at least 28 days notice, ideally day before licence fee becomes due].
It is important that you are made aware that after the above date has passed, I do not need a court order to obtain possession because you will be an excluded lodger.
For further information, please see this Gov.UK page about lodgers: https://www.gov.uk/rent-room-in-your-home/your-lodgers-tenancy-type.
If you are unsure about the contents of this letter you are urged to seek independent legal advice.
I hope this answers your question. If so, kindly rate the answer and provide feedback.
If you have any further questions, please do not hesitate to ask.