In reply to Paul Kerr:
I'v travelled on the Eurostar Lon Par with axe and crampons at least once a year for the past 4 or 5 years. Never had an issue.
There was a wee bit of a palarver a few years ago due to the vauge and stupid policy wording. And there was a letter from ES to the BMC which stated mountaineering gear was ok, or something like that. It was on the BMC website, hopefully still is. We took a copy to wave at any over enthusiastic security, but have never needed to.
ES don't allow locking knives of any length. (Lost an opinel, sigh).
For Par GdN to GdL you'll want about an hr to be safe, it takes longer than you think to get off the ES and walk through the station.