I'm wandering vault 87 looking for the GECK and seem to be just going round in circles because there's not map marker giving me a clue where I should head, is this normal? (The lack of marker, not me wandering around aimlessly, which I do all the time)

There should always be a quest marker. Check your Pip Boy and make sure it's your active quest.

Go back and talk to Fawkes, who will get it for you. Or, you can go get it yourself, but be warned, that radiation is massive. MASSIVE.

Thanks for the replies, it was the active quest but no marker until I found Fawkes, perhaps finding him triggers the vault marker.