Home office expenses - proportion of mortgage interest

Hello, I have been using a room in my own home to manage my property business affairs and would like to claim a fair and reasonable portion of my household costs as a legitimate expense to the property business. I am advised that I can actually claim for a portion of the mortgage interest on my own home where the room in question is, so long as it is in line with the proportional costs mentioned. I am using traditional accounting and not cash basis. I understand from reading HMRC manuals and also from the Finance Act Section 24 (272B) that the restriction on finance for interest relief only applies to amounts borrowed for the acquisition, adaption or construction of a dwelling. Therefore can you please advise where I would enter the costs associated with my own mortgage, as this is actually a revenue expense relating to clerical costs in running the property business from my home office? Thanks.

Hi,
You are not able to set any of the interest arising from a mortgage on your private residence, as a property expense arising from using part of your home to manage your property business.  
PIM2100 advises what can be claimed as an expense
Thank you.