For anybody interested in having a go / entered in the TDG, which I managed to finish last September, the following might be useful
I flew to Geneva and got the Alpibus/Chamexpress to Chamonix, then the bus through the tunnel to Courmayeur. This appears to be the cheapest way of doing it. Unfortunately from the 1st Sept onwards the bus times revert to winter schedule so any timetables need to be carefully looked at.
The hotels are very friendly; everyone I to talked to, said that the hotel put their gear in storage for the duration of event and only charged for nights spent in the hotel. The manager of my hotel not only did this but acted as personal chaufeur as it was 4 km away from Courmayeur.
On the event, take teabags and some powdered milk - the lemon tea provided is quite acidc - I just drank hot water in the end.
It's worth taking breakfast/muesli and some Mountain House meals. They bragg it's a multi national event but haven't yet told the caterers.
I walked the event in 148 hrs 5 min, with an average of 1.5 to 2 hrs sleep a night - no halucinations at all.
A really great event