I have a PDH morgage with a 100k remaing at effective interest rate of 2% (part tracker), current market value 350k. I want to move to a larger property(cost 450k) to use as family home and retain original property for rental income. If i borrow equity of 90k on current property, can i offset mortgage interest tax releif on what will then be a BTL at expected interest of 4.9% on the 190k, or do i not qualify given the mortgage original purpose was PDH