What type of Morgage should I get ?

Spazpeker

Slightly complicated Question but here go's
my goal is to pay the least amount of cost over a 3 year period

I currently have a Mortgage free house in scotland worth Approx £450k

I also Purchased a flat in Edinburgh in my Daughters name with a first charge on the land registry to me

the flat cost £250k and I have spent approx £20k on it and a lot of time and energy worth £270k

I have just had my offer on a building plot accepted and need £200k
I would like to get a intrest only mortgage on my Daughters flat, to fund the land alowing me to sell my property to fund the build when all the plans / warrents are in place

my circumstances dont fit the usual tick boxes, and like everone else i am looking for the option that costs me the least