DS1 used to suffer from up to a dozen night-terrors. We had a formal diagnosis from a very well respected paediatrician, who said DS1's parasomnias were amongst the most severe he'd encountered and that our only hope was that he could grow out of them by 9 (diagnosed aged 4) but that we should prepare ourselves that he probably wouldn't. And could well add sleep walking to the list so we'd better buy some window locks PDQ.
In desperation we self-referred to Millpond. Our consultant was amazing. DS1's night terrors are still present, but reduced to perhaps one per week (from ten or so per night). Her advice contradicted everything my instincts were screaming out to do, but by God she was right.
Used Millpond twice, although both times with younger children. Worked a treat for DC1, who went from a dreadful sleeper to sleeping through the night within about a fortnight (I chose a non cc option), and has done so ever since. Worked a little bit for DC2, but he then regressed at the next possible opportunity (illness / teething / full moon...) so can't say that we saw a long term improvement. That said, I am a bit of a soft touch where he is concerned so probably didn't follow their advice to the letter, and he fundamentally doesn't seem to need sleep.