can i drink say 1/2 the coffee at 8am then the other 1/2 at 11am or do i have to get it down in 1 go?
That's no problem, drink it however you like. Only problem will be that it may cool down and not be as tasty, but that's a matter of opinion.
If i'm travelling i often pour it into an insulated mug / thermos / type thing and sip it through the day.
If that's all your having (plus i'd recommend you drink water), then it works great to keep you fuelled.