Opening your house to paying guests is first of all an expression of a certain attitude towards life: the desire to get to know other people and offer them hospitality. Running a B&B also makes you more conscious of the region where you live more and appreciate the possibilities, tourist and otherwise, it offers.
It is quite an attractive way to combine work with pleasure.
One thing is for sure: it is an entirely different way of life from the one you are used to at home.
One thing is for sure: the Loire valley is extremely popular with English holidaymakers, not in the least because of all the cultural and historic attractions it offers as well as its gorgeous countryside. It is also very popular with English expats. It is not a very long drive from the UK and there are regular flights from Tours to London.
The income you may realise from running a B&B depends, of course, on the effort and amount of time you are willing to put into it. Do you want to spend day and night on maximizing you income from renting rooms, or is it just a nice way to earn a bit on the side?