Ohh I am from Bury st Edmunds (though now living near Salisbury).
Try the Bury pacer web site, they have some running routes on there, i think one is 10 mile but didn't look that closely. Nowton Park is had a trail that many people run on, but i am not sure how far it is.
didn't live on the Best western side of Bury. But The Kings forest near West Stow is also very nice if you like forest run.
SS
And no, there are very few hills in bury.