@Somnolent:
In the LEL website, the zip file in the "Overview" hasn't the elevation data, but if you download one gpx at a time from each section, you'll find the elevation is still present. I say still because I assume that these are the original ones, and that the zipped versions come from them reducing the bytes as much as possible, leaving out the elevation for this reason.
I fully agree that ascent is always a guess: that's why I consider 20% an acceptable error margin.
Where lumpy roads have tunnels and bridges, many websites overestimate the ascent because they ignore them and think that your route climbs the mountain instead of passing through it with a tunnel, and goes down to the bottom of the valley instead of crossing it on a bridge.