OK, I did not know this, so had to spend an hour researching it! I really have little better to do!!
I think the group is credited in the UK as "American Wind" to differentiate them from other groups called or using "Wind" in their name - like the German prog-rock band "Wind" - the group appears to have been just know as Wind, and did not tour or perform live. It is likely the members of Wind changed between recordings, there seems to be no reliable information on who they were. Presumably the writers of "Groovin"; Bo Gentry, Kenneth Laguna, and Paul Naumann, performed on the original track.
According to IMDB (almost always accurate, although I've passed a few edits to them myself!) Harry Pitch is credited as playing harmonica from 1973 to 2006, for 255 episodes.
1. Wikipedia says Mr. Bloe was the name given to the musicians who performed the single "Groovin' with Mr. Bloe" -
2, discogs.com, says Mr. Bloe is an alias for the British composer Zack Laurence -
I think both of those are wrong as they post-date the original recording by Wind, they're only involved in the DJM recording!