Tony's answered the question, Tandh, but I'd like to add a point about finishing.
Fire-resistant plasterboards do the job well. It won't catch fire... but how do you finish it? Ordinary Gypsum skim will crack and probably start to lift after a short while subjected to surrounding heat. 150mm is the minimum clearance behind a woodburner. Skim just can't handle that.
Leave the board un-skimmed by all means, but you'll have to be creative at the outside corners... but it can be done. Plain board can be painted of course.
Lime render & skim is a good one. It will suffer from fine cracking eventually, but not too badly... and it's easily repaired if it does.
A more pukka, substantial solution would be "Supalux" board....
https://www.travisperkins.co.uk/Promat-Supalux-9-0mm-x-1220mm-x-2440mm/p/556001
Looks good plain, and painted. No plastering required. Again, though, corner detail is tricky.
"Masterboard" is another one.