Thank you for the advice, and the very kind offer Poita.
Before I allow Poita to go to the effort and expense of sending me a cable, I'll wait and see if anybody near me has one and can spare the time to help me flash the controller. That way nobody is out of pocket.
In the meantime I'm encouraged that it ought to be a simple fix. I know the scope was working before, so it's not a total dud!
In other news, I had lent my Edmund Astroscan to a friend some time ago, and he randomly returned it today (apparently his wife wanted her laundry shelf back!), so I'm not without a grab and go scope. I'm also not without clouds, so I guess there's really no hurry!