The original ARM was inspired by and designed on the 6502 (in the sense of they visited Western Digital and realized the designing a CPU was actually feasible for a small team, them emulated the design on a BBC Micro with 2nd processor) but IIRC Sophie Wilson stated they have no actual technology in common.
I was very confused here. Western Design Centre, not Western Digital. WDC is still around [1] (or at least the website is up - it was last updated two years ago according to the front page).
For those unaware, the 6502 design was largely the product of two people: Chuck Peddle and Bill Mensch.
Chuck Peddle was an ex-Motorola guy that was on the 6800 team but was dissatisfied that Motorola was unwilling to bet on a much cheaper chip aimed at the mass market (the 6800 was around the $250 level before Peddle left; the 6502 debuted at $25 I believe).
Bill Mench was/is by pretty much all accounts a near super-human layout guy. At this time chips were still laid out without much, if any, computer assistance, and prototype turnaround was slow and expensive, so he was a major asset by cutting the number of prototypes needed (the legend - no idea if it is true - is that he had an amazing run of 9 or so designs that came back working on the first try; far simpler designs than these days of course, but to have any come back working on first try was uncommon).
Jack Tramiel at Commodore (who bought MOS) was always penny pinching, and so Mensch was able to retain rights to produce his own 6502 derivatives, and founded Western Design Centre, and have continued designing and selling related cores ever since.
Yes, you are correct. The team from Acorn as they were then visited and realized that they too could do this, it didn't need the resources of a giant firm. Of course they already had an excellent track record.