I've entered this event today, bearing in mind I've lived in Tonbridge all my life I thought it best to give it a go!
Just taken a good look round the course and thought I'd pick up on the undulating/hilly question:
Within 1/2 mile of the start is a long slow climb of a decent gradient, followed by 2 short sharp but very steep hills with the benefit of a downhill immediately after.
After a relatively flat mile or so there is a long steep climb into Leigh before a very steep downhill under the railway station into the village.
From here you head out for several miles of relatively flat nice tree covered countryside before heading back into Leigh from Hildenborough.
You then rejoin the route for a final 2-3 miles back into Tonbridge covering the same route as before...so you'll have a couple of absolute killer hills approx 10-12 miles in that will be enough to test anyone, but again you have the benefit of coming down the other side of them again.
Looks a good choice to me, the only question I really have of the course is the suitability of sending all the runners up and around molescroft way, doesn't really seem a suitable road to me and I can only assume its been included to get the distance right?