Bitstreams wrote:
The beams in my cottage have been "painted" with a dark brown
substance that looks like something from those stop smoking adverts
twenty years ago. It's not quite gloss paint (though it is glossy) -
where the Neanderthal who applied it has gone over white lighting
flex, it looks a bit like thickly spread marmite.
I'd like to remove it and get the beams looking a little healthier.

What can I try ?

Simon
Professional sand blasting company, or nothing.

If the beams were new and planed, then they wouldn't be painted. If they
are old and pitted, nothing else gets the paint out of the grain.