It used to be accessible also at https://www.kcl.ac.uk/humanities/cch/langscape, but that doesn't work either.
I've sometimes thought that there needs to be a digital humanities meta-project, whose only job it would be keep websites of old projects running.
Meanwhile we can fall back on the waybackmachine:
https://web.archive.org/web/20181229124047/http://www.langscape.org.uk/search/index.html .
Keith