lynsandtone wrote:Hi, myself and some friends are going to climb Mt Blanc on the 25th September ...
Any advice would be greatly appreciated.

Hi Tone,

although I can't really satisfy your questions, I try to answer since nobody else does.
As for the blankets, phone Gouter hut.
From Bellevue to Nid d'Aigle (end point of TMB) you have to calculate additional 600 m of altitude, most easily done along the tracks, I suppose.
A valuable source of information is also the Office de Haute Montagne, OHM, Chamonix.

Good luck
and write a nice TR in case of success!
Reinhard

Tone, seeing my maps there is a forest trail to Bellevue but I don't think that you can drive up because it could be closed by barriers either in Le Crozat (SE) or La Maison Neuve (N). Take care, weather can be bad on Mont Blanc in late September.

Refuge du Goûter

I think the cable car from Les Houches to Bellevue has closed for the autumn since 17th Sep.