Hi,
It is pretty rigid as there are established guidelines.
1. If you use your personal car for work, and or work away from your main place of business you are entitled to reimbursement of expenses, tax free or within Civil Service rates for unreciepted allowances.
2. You can refund any directors loans.
3. Everything else is pretty much treated as salary.
If your going down the line of drawing a small salary, your probably going to be under your own tax free allowance and probably wont incur a huge paye bill anyway.