My partner and I would highly recommend booking your Tour du Mont Blanc adventure through The Alpine Adventures.
We booked our 12 day multi-day hike relatively late (Feb 26 for August 26 start) and they were able to source adequate accomodation for the entire hike well spaced to avoid very long or short hiking days.
They provided a detailed guidebook and gpx for a navigation app which got us to where we needed to go without fuss, and all correspondence before the hike and instructions on the hike were extremely clear. This included transport options to/from trailheads if the accommodation could not be sourced on the trail and a helpful packing list.
Alexander was our Travel Consultant and he was happy to answer any questions we had and organise a time for a call to go through any details we needed.
We were very happy with the trip and would considering booking our next multi-day hike through The Alpine Adventures.