Opinions on these routes for London to Paris please

[RhythMick]

I'm doing this challenge with a number of people from work, one of whom has published the routes on Garmin. You can view the routes at the links below you don't need to sign up. I'm a bit concerned that the Day 1 route in particular seems to be predominantly just following a main road and I'd like a little local feedback as to how advisable this is please.

Day 1 Route https://connect.garmin.com/course/8418281

Day 2 Route https://connect.garmin.com/course/8418293

Day 3 Route https://connect.garmin.com/course/8418296