Many thanks for your guidance.
For some reason my blower does not play ball. Whether on heater or on aircon I have no fan,.... except, just as I was going to get round to checking fuses it came on, all speeds, and then stopped again after five minutes. All this has meant that i could not prove my aircon until i fixed the fan.
I thought this was a fuse but now, with an intermittent fault being far more difficult to locate, I need to start inspecting connections, resistors, relays, motor brushes etc etc. Damn, I had hoped it would be a simple fix.