Search on Concertina.com produces only one reference to "blind harper M. Henderson" from Dan Worral's "Notes"
Stuart Eydmann's paper on Scottish concertina players is available to read -
It's from pre-internet days, so he may have more information since then. I used to have contact details from when I passed him info about my friend Joe Maley/Jack Easy, can't find at the moment. I have no doubt Joe would have encountered Martin Henderson, though unlikely to have been booked on the same bill!
Good luck with the search.