Commuting to Chamonix from Geneva and onto LONDON

Has anyone done the commute to London (City airtport) from Chamonix? I
see good flights on Friday afternoon (1730) from London returning early
(0755) Monday mornings and am finding it hard to see transport/transfer
companies working with these times. I'll only ever have hand luggage so
don't need to arrive hours before the flight leaves.
Any suggestions on the best ways to do this and potential problems
would be appreciated.
Are there others that might be interested in sharing transport at these
times?
Is there somewhere near Geneva airport that you can leave a car safely
during mid week without having to pay? Might be an option.
I like winter sports a LOT : )~