"Very long waiting times for appointments and..."

I was originally referred back in sep/oct 2014 and my first appointment was pretty quick and things got moving and the staff were helpful when i was there. However the treatment i was on wasn't working for me so on 2nd march 2015 i called for an appointment so we can discuss and go ahead with the next options. I am still waiting just for an appointment i call up every week for any cancellations etc and no one can tell me roughly what the wait is. I keep getting told they are waiting for the next slots to come out but iv been told this for the last few months and surely they can estimate an average time based on how many people get appointments a day to where i am on the list. Its very frustrating and disappointing to just be told 'wait for a letter'.