Hello @David2436
Sorry to hear about your experience.
You are charging people for a service you provide; therefore you ARE running a business.
Just because you haven't registered as a limited company, partnership or as self-employed doesn't mean it is not a business. It is always a good idea to check your lease to see if there are any restrictions, before you set up your STR business.
Options - can you talk to the management company to see if there are options for you to run a business with their permission. You could talk at a housing solicitor and get an initial consultation to see what your options are.