Well... I don't know quite what to say about Steve Crowther. There is almost no information on his website about what he trains in, who his instructors were, who awarded his 5th dan, nothing. That's not usually a good sign. I'm not saying he's bad or anything, there's just not much available information for him. I checked google and didn't turn up much either.
The information available at this address http://s106679294.websitehome.co.uk/dvd.htm
makes it apparent that he's basically created his own style.
Now there is good news since your in Massachusettes. Boston is home to no less than two Muso Jikiden Eishin Ryu Iaido instructors. Cuoung Nguyen is a sandan in the Canadian Iaido Association, which is a daughter organization of the Zen Nippon Iaido Renmei. I've met him. He has a lot to offer as an instructor. Nice guy to boot. Warren Stanley-sensei is a Rokudan Renshi and student of Honami-sensei, who I understand was just awarded his Ninth-dan. Stanley-sensei's ranks come through the Zen Nippon Iaido Renmei. I have met him as well. His Iai is outstanding. He's probably the top MJER guy in your neck of the woods. Certainly within the ZNIR/Seitokai branch of MJER .
Now to clear things up a little
The MJER Seitokai is the organization led by Ikeda-soke, 22nd leader of the style. The Zen Nippon Iaido Renmei(All Japan Iaido Federation) is an umbrella organization consisting of the MJER Seitokai and members of several iaido ryu-ha. Both organizations are rather large in Japan.
You can get in touch with Nguyen-sensei through http://www.bostoniaido.com
To get in touch with Stanley-sensei send me an email. He doesn't have any online presence, but I can put you in touch with one of his students.