In reply to Dave Todd:
If you're driving, consider booking a travelodge right by the tunnel or ferry. It means you can get the UK leg of your journey done the evening before with no worries about missing your slot. It also gets you the right side of the "Operation Brock" M20 contraflow which causes carnage in even moderate traffic.
Also, use your satnav or google maps to take you through Paris. The road system through there defies human understanding and its very easy to get horribly lost in an instant, satnav can save a lot of upset here (worth paying for data roaming for that alone).
If you're looking for something different for a day, look at the Sentier 25 Bosses, a 10 mile marked trail around the hills of the 3 pignons (900m total ascent!). It takes you through natural obstacle courses over/through/under boulders at every opportunity and has great views across the forest.
The reason the JW (and every other) guide has the odd different circuit to those on the ground is that circuits are periodically repainted and changed. JW guides are a bit bonkers, but they have by far the best coverage in the easier grades.
Font is amazing, have fun.
Tom
Post edited at 10:08