Hi gdosteopathy,
Thanks for your post.
I believe that this can be done through customising the Appointment List report. I am unsure how much work is involved in doing this so there maybe a charge. I will find out for you and post back on here.
Alternatively, you can run the Appointment List report and group by Appointment Type. This will then give you the number of each Appointment Type and you can work out the average from there.
Many thanks.