Mont Blanc Alpine Tunnel

Dewint

Currnetly intending to travel down to Italian Lakes (Lake Orta) for wedding (not ours) in May 2015.  Obvious route from Calais is via Geneve (French Side) via Chamonix Mont Blanc.  This would save around 250 miles on the single trip via the Brenner.  Has
anyone out there any experience of traversing the Mont Blanc. Have not issues with the French side as lived on the continent for 6 years. Will be making this into a longer holdiay and will be coming back via Brenner.  But have no experience of Mont Blanc Tunnel.
Has anyone any knowledge or experience of this pass.  Will be in Bailey Approach Motorhome.