The problem in the UK is that companies can still deduct the mortgage interest, this puts people who buy property to rent out at an advantage.
[1] https://en.wikipedia.org/wiki/Mortgage_interest_relief_at_so...
Not just companies in the usually-understood sense; private landlords can deduct mortgage interest on the property they let as an expense to reduce their tax bill. No need to set up a company or actually declare yourself as self-employed or whatever. (Conceptually they are running a business, but there's no need for a company.)
I'm not sure what you mean when you say these people have an 'advantage'?
People who buy-to-let are not in the rental-income business, they are in the business of acquiring property, because property prices are sky rocketing.
People with a job trying to get on the property ladder pay mortgage interest with wages. People with second, third etc. properties deduct mortgage interest as an expense.