Actually ypu can find the loop here and on google earth the elevations: http://www.beyondthelimitations.co.uk/resources/GloucesterMarathon2012instructionsDMv2.pdf
The highest elevation is 34 meters which you reach only in one location , the lowest 10 m, the distance of the hill is about 0.7 km so about 3%, pretty flat thus....
Actually Portsmouth was not too bad, a little muddy but flat and not too slow. How much is the elevation differnce of the hill in Cloucester?
Ok, that should not be too hard, hope we can deal with that and have a quiet day...
How is the course? judging from last year's times quite tough...