Whirly,
The French low-level military corridors are a pain in the butt and lots of them cross your route. They are generally not active at weekends, which are the only times I've crossed France.
Hot and high can be a problem in the Alps with an aircraft like a 150. A C172 or Warrior, can't remember which, went down at Gruyeres last year (2300feet amsl, temp >30 degrees), stalled into the trees on takeoff, all 4 killed (the number of POB on board says it all).
A C152 failed to clear the low pass a couple of miles after taking off Easterly at Saanen (3300 feet amsl, also last year, both killed.
Something to think about if you head off to a mountain strip on a nice day for a look-see, stacked up with gear!
Have a great trip,
QDM
P.S. The heavily loaded Dakota staggering off from Saanen in > 30 degrees last year would have made your eyes weep.