By pass your GP. Ask your diabetic clinic nurse to refer you to the ED outpatients. Once you get an appointment, ask to try Viridal.
It's a small self-administered injection with a very fine needle that you barely notice that you inject into the side of the shaft and is mega. You will get a 'diamond-cutter' erection that lasts at least an hour even if you pop your cork to early, and you will get secondary erections for a couple of hours after (who's complaining?).
It is excellent and has no side effects (such as flashing lights, blue tinted vision etc). I'm 57 and been using it for 3 years now.
But unlike viagara, where you usually get adminstered 2 doses a week, viridal is more pricey so the spoilsports only give you 4 shots a month.