Hi rknrolls,
I'm glad to hear that you're considering our classes in London, where we've had quite a bit of success over the years. Amit Kakkad, the instructor you met on Monday, is one of the best GMAT instructors you can find worldwide. He was named Instructor of the Year for Veritas Prep based on his student evaluation scores and feedback, his students' GMAT results, and his contributions to the Veritas Prep lessons and instructor community. In fact, no less an authority than
Dr. Lawrence Rudner, a Vice President of the Graduate Management Admissions Council (and the guy who's considered the "brain" behind the GMAT) who met Amit at a GMAT event in London, made a special point to seek out our Veritas Prep team at a subsequent event in the U.S. to tell us about Amit (I'm paraphrasing): "That guy's sharp... he really knows this test inside and out." I think some of the other test prep providers on here even overheard the comment!
Naturally, I can understand your concern about learning the verbal portion of the test from a nonnative speaker, but I can personally vouch for the fact that Amit -- a PhD candidate at London Business School -- understands the verbal section of the exam, and how to succeed on it, more than anyone has a right to.
We typically do want to have the same instructor teach both your quantitative and verbal lessons, as there is a definite benefit to your having one guide for the entire exam to help gauge your progress through homework and practice tests and to enable to you to ask questions regarding lessons as they come up, rather than waiting until a "math night" to ask a math question. Furthermore, you'll likely find that there is quite a bit of overlap between the logic required on either section (you may recall this from the Arguments lesson that you attended -- the Data Sufficiency math problems are essentially Critical Reasoning logic problems with a mathematical emphasis and a twist in the way that they're asked). Having one instructor, and in particular one as knowledgeable and experienced as Amit, to help alert you to errors that you may make on either section based on your performance on the other, should be a strong asset to your preparation.
I'll allow
MGMAT to address your questions regarding their program and affiliation with Kaplan. I do know that they're pretty new to the London market, but hopefully you'll find a London
MGMAT student on the forum who can share his experience with you to aid in your decision.
Let me know if you have any more questions!