What hourly rate can I charge to clients?
The hourly rate you can charge will be determined by your employer or you if you are a sole practitioner. Your rate is likely to be based on your skills set and experience. There are no set rates as it's generally considered a supply and demand issue - the more highly regarded you are the more demand for your service, thus higher rates can be charged.
That explained, should a court carry out an assessment of costs, it can have reference to the 'Guideline Hourly Rate'. Whilst these are guidelines, and do not prescribe hourly rates, the court and parties can use them for a reference point.