Doesn't sound to me like you should have anything major to worry about - you've put in the training, you've done the long runs, and you say you were pretty comfortable on them too. 4hrs30 doesn't strike me as over-ambitious based on the training paces you mention, but it's good that you're not too hung up on achieving it. Don't rush off too fast at the start; think slow and steady and you should be fine.
You've done loads more training than a lot of the people that are on here asking 'Have I done enough?' the week before their first marathon. It's not my first marathon, but I'm doing Edinburgh too and you've done loads more training than me - my last long run was 18 miles over a month ago as I've been resting a pulled calf that's been slow to go away. I'm totally confident of finishing and in roughly the same time that you're hoping for.
Does that make you feel a bit better about it all? 
Edited: 18/05/2012 at 18:29