Home office expenses

I work from home - I have an office and photographic studio, so am trying to work out what I can claim as household expenses. We no longer owe money on our bond, so it seems like I can't claim anything there. I understand I can claim a portion of rates, water and electricity. Can I also claim a portion of the homeowners insurance and the security (armed response) costs?

Do you have a separate office which you work from in your home?

We converted a large room into a photographic studio and another room into an office, but they are both in our home. I use those two rooms exclusively for work purposes now.
Thanks.

That's perfect, what you need to do is measure the size of the office as a percentage of the size of the house and then apportion the expenses related to the office using that formula.