Blower control module has failed.....that is a classic symptom of it....it is located right to the left of the blower motor under the dash, two screws and an electrical plug to remove it from the blower box. The system will default to high speed all the time when they fail.
Thank you so much for replying. I will attempt to dig it out and replace.
I feel a bit guilty swooping in here for answers (after searching) and disappearing again for a year at a time. This has been a good car, my kids drive it. I just tickle it once in a while to keep it going.
found it, pulled it, no way of knowing if it's the problem but I see one on ebay so will procure, I think I'll interrupt the circuit with a simple toggle switch just to turn the fan off and on in the meantime.