Anthony, depends on your field. One of my older brothers (who ranks higher than me on google if you search for my name) runs a consulting business for .NET applications and he has on occasion earned anything to to £400/hr for his services. A more regular and generic rate to charge would be a usual freelance rate of something around £30-50/hr but it all really depends on how specialised the consultation is that you're providing. And yes, per-hour is generally the way to go.