I found the same thing recently. He had been head down in an L formation for weeks and then all of a sudden at my 37 week appointment he was breech! We discussed the options and I decided to hold off on the version because this guy has so much room to move right back around if he wanted to. I tried some of the positions, too, but they were very uncomfortable and didn't seem to do anything. I received acupuncture and moxibustion and it seemed to get him on the move, but then he was transverse for a few days (a bad position, but technically a good sign because it meant he was making efforts to turn) and then he went head down! Some of the things we also tried (who knows what helped and what didn't): having DH talk to the lower half of my belly, putting a warm rice sock down by the pubic bone, sitting in a warm bath (since the water only reaches my lower belly anyway) and perhaps it's weird but I found he did a lot more moving when I would lie on my side so I would drink a coffee --which makes him pretty alert-- and then lie down for a while and watch him roll around! My midwives also suggested putting ice or something cold where his head was and putting a heating pack by the pubic bone so hopefully they turn towards the warmth, or using a flashlight to attract him. ::shrugs::
I'm still going for moxi weekly and at my last appointment it was confirmed he is head down, but he is still so mobile I have to keep on top of it. Lots of walking and squats to hopefully help him engage head down. I am 38 weeks now and measuring about 40 cm, and he is only about 6-6.5 pounds but absolutely swimming in fluid. A couple of weeks ago I really thought I was going to go into preterm labor because he was engaged and dropped, I was having TONS of potent contractions, and many other pre-labor symptoms, but then the little bugger turned over and everything came to a halt. Now it seems he's nice and cozy in there until his due date (the 18th).
Anyhow, just thought I would share that I feel your frustrations and concerns and I'm thinking good sunny-side up thoughts for you!!