On 9 Aug, 21:38, Tom wrote:
I'm looking for a quite slow rotational speed electric wirebrush,

Maikita do one. Few hundred quid to buy, but you can hire them.
Looks like a cross between a flapwheel sander and an electric plane.

I'm also after a decorators' hook but much more robust, for scraping
100 year old sooty plaster-like material from a fireplace opening.

Sandvik do a big scraper hook with carbide edges. Great thing,
particularly for tarry stuff on floors.