Maybe I wasn't clear with my question and I'm sorry for that.
At the moment I'm not planing to move. The whole process is for the future.
Let say in 4 years, at the same period of time, I want to move to my new residential house and then put this one in BTL.
The question is, should I put my spare money into my savings account or to invest them into the mortgage (10% annual repayments) and other improvements (extension) of this house ?
(I'm trying to find out the process behind moving the house to BTL and releasing the equity from this one so I can plan for f