Your post is rather confusing @George1837
1. If you build a summer house in the back garden and you want to use it for commercial use - you need planning permission from your local council. It doesn't matter what your view is, what matters is what our planning regulations are. When you are running a business which an STR is the regulations are clear.
2. If your landlord is the housing authority or social housing I highly doubt in your lease you would be able to operate a business from your premises
Presumably you have checked your lease?