I took some mince I'd frozen from fresh out of the freezer to defrost in the fridge but it was still mostly frozen when I needed to start cooking it. I fried it off, breaking it up as I went and then put it in a dish with stock in the oven for an hour or so....it is ok to cook from frozen like this isn't it?

Yes, it is.

Great, thanks

Cook from frozen but make sure all moisture evaperates, it wont start to cook properly till then.

Is it minced beef?

Now be fair, given latest new, how is OP supposed to know that?

lol