Chrissa1, just a thought, you say you should charge 1/2 the hourly rate 'just in case' what if other companies followed the same principle, say the RAC, or British gas did the same. What does your average gas fitter or car mechanic charge per hour? �20??(would love to find one that cheap), so you get insurance with them, and they charge you 1/2 their rate/hour for this, so thats 24hrs*30 days a month=720hours*�10=�7200/month, you'd be happy to pay this would you?
Hope this helps.