Most will crack but not these bad boys.
I sort of get fed up with this, but here goes:
A pizza stone is a ceramic material and WILL crack if it is subjected to rapid heating and/or significant temperature differentials. This, in my opinion, will also apply to these "bad boys" (unless there is something significantly different about their composition?).
But, at 40 quid a shot (?), go for it....but I wouldn't!

But I do quite like the idea of a chimnea with a "tilting/hinged" chimney