Hello John,
I read your posts via the Permies daily-ish email.
We too are on clay soil.
1. About the French drain; you say you put it with the holes downwards. I'd think it might work better with the holes up (and with geotextile on top, filtering away any soil particles), allowing the water to seep into the drain and flow away on the 'floor' of the drain? I haven't tried it, nor do I have any theoretical knowledge about correct use of it, it's just what pops into my mind now.
2. We thought about putting in a French drain, but I was lucky to have a conversation about the here on Permies, and went for wood chips instead. It has worked really well! You can read about it, and see a couple of photos
here .