"Kept waiting for no apparent reason"

I arrived at the Motherwell Health Centre at 12.55 for 1pm appointment in the Sexual Health Clinic.  I took a seat in the waiting room.  From the waiting room I could hear conversations of staff behind the reception area that were undoubtedly of a social nature - voices were raised and there was much laughter.  While I was waiting I read the various notices asking patients to "be patient" if the clinic was running late.  At 1.15 the conversation from behind the reception area came to an end and various staff nurses appeared and began to call patients in for their appointments.  The nurse that called me in did so in a very casual manner.  

Whilst I appreciate that 15 minutes is not a desperately long time to be kept waiting I objected to the apparent lack of genuine reason for this.  I found the behaviour of the staff sincerely lacking in professionalism and disrespectful.  This was of course worsened by the presence of posters somewhat abruptly stating "be patient".  I understand the need for these posters but could I suggest a more polite tone - "we appreciate your patience" perhaps?  Also, if the clinic is asking patients to be patient they should also be doing everything possible to ensure their clinic is running on time.