The Pierce Piano Atlas lists the following serial numbers:
1923 - 3700, 1925 - 24100.  From this I would assume the date was
around 1924.  Marshall and Rose was established in London in 1907, so
you would be correct in saying the piano was originally from England.

Concerning the working dangers in this project, I would at least use
a respirator when working on anything this powdery.  If you have a good
exhaust system in your shop I would also have that on when working on it.

Have you tried using steam heat to remove the pneumatics from the boards?
I find using an iron and damp cloth many times will loosen both layers
of the cloth with very little wood coming off.  The wet cloth also
soaks up the powdery dust that comes with removing old cloth.

Clarence Zeches