For private tuition From 1st September 2009 until the end of August 2010 the Musicians union suggested minimum rate is £27 per hour. It is only right that you charge no less than that, in order to not undercut other teachers on the basis of fees or to under value music teaching on the whole. 

Understandably if you are new to teaching privately you may wish to charge less in the early days, I believe you should state the reason for this as being that private tuition is new to you.  

If you have a lot of performance experience or something very unique to teach or incur expenses you should definitely consider a higher rate and don't under value yourself.

It is advisable to have a written contract between private students and yourself to ensure that you know where you both stand regarding payment, cancellations and the like. 

For group teaching and workshops there is unfortunately no suggested rates from the MU etc. I shall be making enquires about the Musicians Union having a Community music section. I would say the minimum you should charge for such work is around £35.

For contract work: If you are working under contract for another organisation the rate of pay is liable to be less per hour but the contract will ensure you work and pay and liability etc is in the hands of the organisation you are working for.

Mates rates: A lot of private tutors offer Mates Rates for friends etc, these rates are at your discretion but make sure that you state that's the rate for them because you know them, make sure that people know that its less than your usual rate. You are more than likely to get work from friends/colleagues etc of friends etc, so make sure to charge friends of friends - that aren't your friends, your usual rate.