Rent increase - how do I go about doing this

I’m not trying to persuade you as you’ve clearly already made up your mind, but for the benefit of others who might be reading, my view is that when tenants say they need to move for work or because they can no longer afford the property or any other reason really, it is not sensible to just just say no and hold them to contract, partly because they frequently just stop paying and you have the hassle of trying to sue them for the rent and partly because you are potentially leaving an angry and reluctant tenant in charge of an asset worth hundreds of thousands of pounds and you may be discovering aspects of their revenge for years to come.