Hi ABank
I think it's useful to have such ideas, but they have to be grounded in reality. You will need to get your tax consultant to specify how it works.
If it's an investment property in negative equity, the company could only buy the property at its current value and could only borrow the amount of its current value. You could not transfer in a loan in excess of the market value.
The supposed advantage of operating through a company is 12.5% Corporation Tax. But if the property is in negative equity, you are probably not making rental profits anyway, so tax doesn't really come into it.
If you are self-employed and you want to operate through a company, that is a separate decision. Opinion is divided, but I believe that in general, you are better off operating as self-employed and not as a company. However, I haven't reviewed that in the light of the changes to the tax relief on pensions, so it might be different now.
brendan