@Renata545 you can pretty much claim all running expenses - heating, lighting, insurance , cleaning, laundry water rates etc etc. You can keep things simple by just declaring everything on your tax return. You then get the standard 12570 personal allowance and then pay 20% tax on the rest below 50000.
You should also look in to business rates rather than paying council tax.
ONE DOWNSIDE of any type of rentals is you will pay capital gains tax when you eventually sell the property.