I just thought I'd update. I completed the Marathon in 4:33 so overall very pleased but very similar experience to daeve, In hindsight I didn't get enough long runs in only one 20 mile before the event. I got to 18 miles in 3 hours then it all went to pot 1:33 for the next 8 no injuries just dead legs, Great event Barcelona, Rome next!!
I'm a novice veteran runner (47),I completed the Great North Run this year in 1.53 (first race) and have entered the Barcelona Marathon this will be my first Marathon what would be classed as a respecatble time to aim for?