Perrin has a book describing his process and research. It's detailed to the point that you could do some of it yourself or share with a physio or osteopath to see if they could do something similar. It is lymphatic drainage+ spinal alignment + cranial stuff with an aim to drain lymphatic fluid from the head/brain. I'd heard about osteopathy for ME and initially it made no sense to me until I read this piece at Health Rising and listened to the interview with Perrin linked in the piece. Some bells went off and made me think it was worth trying with my daughter especially since there happened to be a Perrin trained osteopath 10 minutes from where I live. I seemed like a "nothing to lose" kind of thing.
I will say that for most people it isn't a "cure" and very likely helps much more if you're young and/or haven't been ill for decades. It's something to do in conjunction with other therapies (pharmaceutical, herbal, lifestyle, etc.)
Also, update on my daughter--she's now on midodrine and stopped the horse chestnut. She's had a bad flare over the past few months and her consultant thought it made sense to go to something more powerful. Flare was mainly due to hormonal issues, I think. She has serious POTS flares pre-menstrually and during periods and possibly endometriosis. She was put on the worst possible (cheapest) continuous birth control by her GP and was having breakthrough bleeding all the time. She's now on a higher quality birth control pill and on midodrine and she's back to what seems to be full wellness...for a while, anyway. It never seems to end, really.