Basic travel questions from novice traveler

[Carla Dolce]

I am traveling from USA (Denver) to London then to
Biarritz and on to St. Jean Pied de Port to start the
Camino.  I have never traveled outside US.

My only luggage is, of course, my back pack.  Because
of the many straps and strings on the back pack, I am
placing it in a rip-stop nylon laundry bag to check it
at the airport.  Is this a reasonable way to take the
back pack to minimize damage?  The only alternative I
can think of is a cardboard box.  Any suggestions for
the best way to check the packpack at the airport will
be appreciated.

(I don't think I can carry it on board because of the
Swiss army knife nail clips, etc.)

Also, I am taking many vitamins and supplements, which
I repackaged in small plastic baggies to avoid the
weight of the original containers.  Does anyone know
of any restrictions on getting vitamins and
supplements (including the hormone DHEA) past customes
in London or Biarritz?

Thank you!
CJD