Yes it's at Hauxley nature reserve - or it was; they've had bother with vandals and fire-starters over there in recent years.
Now those fossil trees - still in their growth position - often appear in the roof of roadways in deep mines - and dangerous they are too. they can drop out and do some serious damage. the core would be solid stone like the one shown, but around the rim would be a few millimetres of coal. I think it was this thin shroud of coal that made them unstable and prone to sliding out of the roof. Not nice objects.
I'm sure we used to call them a "catteringarse" (!) [Alan_J can you remember this term or have I got it wrong?]
On this (US) website if you scroll down to the fourth picture you will see one hanging out of the roof. What they have done there is put a roof bolt through it to make sure it stays put.