Thanks for the replies here. For some reason I do not always get notification about replies on threads so I missed these.
I agree that TG2's default atmosphere gives generally natural results, at least definitely like the kind of atmosphere we get in the UK - thick and misty. I don't know about other places though. I have experimented a lot with this and found that the open space kind of feeling you see in say Mojo renders is because there is less atmosphere or haze going on at least certainly at higher altitude. If you want this it's quite easy to just reduce the haze exponential hugely and increase it's density. This opens up the space immensely and the low haze gives a good sense of distance but you also need to set higher samples so as not to get grain if you're creating thick low level haze, like you often see in Mojo.
I will wait to see how things go with the shadows.
Thanks.