As it is my home course, I know from long experience that the ups and downs take their toll over the 2 laps. The worst 'up' is towards the end of each lap, at 6/12 miles. Although there is nothing hideous like in the Marlow Half, the many small undulations do not really allow you to setle to a steady pace. As your map shows you gradually climb until about 3 miles on the first lap.. From thereon to about 5.5 miles is the time to claw back some of the lost time. Beware the nasty but short hill after 5 miles followed by another short downhill and then the haul up to the end of each lap. The steepest hill of all is the bank 200 yards after the start and shortly before the finish!!
Hope this helps. Enjoy the run but do not expect a PB.