Do you know whether your T has some sort of formal agreement with the lodgers, such as a house share agreement? If he does, what does that say about changing the T that the lodgers report to.
Someone with better legal knowledge than me may disagree, but it may be an idea that you arrange to replace T on a specific date, you move in, T moves out. At the same time, you arrange that the lodgers sign a house share agreement with you and you effectively become owner in residence with 3 lodgers.
I offer my advice freely, but I am not an expert, solicitor or judge. It is simply my experience of being a landlord and what I have learnt along the way. I make no warranty for my opinion.