Am I mad to eurostar in on the Saturday and stay over to see the finish? What time would we need to be at the finish point yo get a decent view?

Friday I reckon….

Depends what you mean by decent position. I’ve arrived at Champs-Élysées Clemenceau metro station after the start of the stage and still been only a couple of people back from the barriers by the time they were going past. If you want the best possible position then you need to be there much earlier before they barrier off all of the best bits. There’s seating near the finish line, but I’ve never been early enough to see if it’s a free-for-all early on or if you’d need tickets anyway.