@Ian41080 Airbnb will inform HMRC or your earnings and you will pay on these however:
If you are a Furnished Holiday Let (105 nights/ year rented, available for 210 then you can
1) offset mortgage interest
2) offset costs of running the place
3) Contribute to a pension
4) If married split the earnings anyway you want with your spouse
Just search FHL on gov.uk
What is a bit unclear to me is what gross earnings you should declare. Is it what the guest pays or what you charge? Either way the Airbnb fees of 14.2% guest and 3% host +VAT are deductible from the relevant gross earnings.
Perhaps get an accountant to confirm the above