Any question answered...

sitting at my kitchen table 15 hours a day

This would wind me up no end. If you don’t need the money, I would terminate the agreement.

Then start afresh.

You’re not getting anything from the current arrangement.

I honestly care much less about the money and more about having someone I find easy going

1 instead of 2 if you're not fussed about the money, but with enough of the notice from 3 to make it fair and legal.

Redacted. :)

other random invented reason

"I need the space for my own project" is uncontestable

I guess terminating your rental depends on what Tennant they are.

https://www.gov.uk/rent-room-in-your-home/your-lodgers-tenancy-type