I think that you are paying very far over the odds for medicals if you pay £400 per year. I paid £105 for a class 1 including this time all the extra bits (hearing etc).
The figure for rating revalidations could not be an annual one coult it?
Since you have your own building and thus the requirement to insure it I would not include that in an hourly cost.
What about the groundschool income, income from membership fees and all the other bits.
If you are a self employed instructor working for one or more schools then you have had bad advice if those are your typical annual expenses!!
Regards,
DFC