Great questions, thanks.
Best place in UK for this type of surgery is Spinal Foundation, founded by famous dr. Martin Knight. Other great places are Wooridul Spine Hospital (Korea, dr. Sang-Ho Lee and his team), Desert Institute for Spine Care (USA, dr. Anthony Yeung), dr. Thomas Hoogland (Germany, I think he sometimes operates in Beta Klinik Bonn), dr. Robert saftic (Croatia, Spine Surgery Croatia).
Its not a myth. If you don't wait for surgery too long, if you had no previous surgery on affected level, minimally-invasive spine surgery (especially endoscopic and laser) can have from 80-90% success rate. Not only in one center. This has been scientifically proven.
I know a lot (and I really mean A LOT) of patients that had great results with laser spine surgery (PLDD). My mother had endoscopic surgery for her failed back surgery syndrome, at it relieved only 20% of her pains (understandable considering the fact that she already had one open surgery).
Don't ever compare micro and minimally. Micro-surgery and minimally-invasive surgery are two different terms that mean different concept in spine surgery.
Your note about rivalry is in place. Biggest "enemies" of minimally-invasive spine surgery are surgeons that:
1. Are not prepared to move on,
2. Don't want to follow advances in modern medicine,
3. They think "its something new", although MISS is around for 20-30 years,
4. Don't have the ability to perform this technically advanced surgeries
I personally know more than 10 spine surgeons. Some of them do MISS, some of them only traditional surgeries... and I tell all this from my personal experience.
If you have more questions, please ask.