hi and welcome to the forum the flat you live in is likely to be fine with the OR if it has no equity he will likely allow you to buy back the BI the other property could be classed as a business and as such is more potentially problematical any equity in it would be required by the OR so if a family member could buy the BI from the OR without having to repossess and sell the house that may be ok it would also depend on whether the rental income from the house is covering the mortgage and what view thw OR took on the rental income towards an IPA
i would suggest you took some professional advice from one of the forum professional experts like mel at jones giles or Paul Johns form RevivUK (link on the left hand side of the page)
Dave
Don't worry or know that worrying is as effective as trying to solve an algebra equation by chewing bubble gum.(Baz Lurman) RevivaUK helped me through it all i can't recommend them enough!!