Doing that sort of work off a ladder is lunacy. A scaffold tower would
seem to be a good compromise if you have sufficient space for one to be
erected and the chimney is on an end wall. A local handyman type would
possibly have a scaffold tower. A bigger building firm are most likely
to go down the H&S route of needing a proper scaffolding to be put up.
You possibly don't need a skip if you are prepared to do a few trips to
the dump and clear up after the contractor.

Bob

I think a roofer would do the job off a ladder. Piece of cake, as you'd
be standing on the tiles most of the time