Very fit people say it is pretty flat, less fit people say it is quite hilly!
Here's the actual profile:
As you can see - there are quite a few small hills, some quite steep, and quite a few long drags. When I first rode the event, I'd be rolling along with a group of riders doing about 20 mph and kidding myself that I was quite fit. Then we'd hit one of the hills and they would keep going at pretty much the same speed and I'd get blown straight out the back and have to chase back on after the hill. It doesn't take much of that to grind you down. Much better to ride at your own pace.
When I rode the event fit, I admit that the hills didn't bother me much but they do exist, so don't let people kid you that they don't!
The 'halfway' lunch stop is actually at 55 miles so don't let that catch you out. I got to about 47 miles and thought I'd try and make up time by going flat out for 3 miles. I ended up limping in after 8 miles feeling like I was going to die! Mind you, you 'only' have 45 miles to go after that rather than 50, so once you are aware of it, I think that it is
A Good Thing.
The 100 km riders tend to be people who don't ride bikes very often so their road sense often leaves a lot to be desired. They start after the 100 mile riders on the same route but then take a shortcut to rejoin the longer route on the way home. What this means is that you suddenly start encountering hundreds of novice cyclists wobbling about all over the road just as you are getting back into the built-up areas on the fringes of Manchester. Watch out! Also, the traffic in the last 20 miles or so can be quite heavy. Don't follow the idiots jumping red lights - I've seen several people nearly get killed just trying to save a few seconds.
Be very aware of a little sting-in-the-tail between Wilmslow and Styal! The road plunges down and then turns sharp right straight up a fairly steep little hill through some woods. If you don't have a low gear engaged in anticipation, you are likely to grind to a halt and have to dismount, and then you'll struggle to get going again!
Oh yes, one more thing - after 40 miles or so (I can't remember where exactly) you come round a sharp bend (RH I think) and there is a farm on your right. Several times when I rode the event there was slurry on the road and there were some serious falls.
I made a similar post on BikeRadar a couple of years ago which includes a map and a GPX file of the route -
link.
Pace yourself, eat and drink plenty and have a good time!