I know this is a stupid question but...!

[Hooplah]

I'm not the most instinctive cook! I have a recipe to cook a casserole on the hob for 3 hours - fine. But I want to put it in the oven today and was thinking of cooking it for the same 3 hours on a very low heat (120, fan). Is that about right?! Does it even matter with a casserole?

Sounds about right to me, what meat is it?

It's beef - I just don't want it coming out tough and chewy!

I'd cook it at 150C

Maybe too late but 120 sounds too low to me, agree 150 fan better.