In reply to BuzyG:
In the same way you would add a route, at the bottom of the hill page there are two buttons "Add a missing route" and "Upload a file of missing routes".
You can also create a Route Card, which is a more detailed walk, and once passed through moderation, will be on the UKH Route Cards page here:
https://www.ukhillwalking.com/logbook/r/find.php
Hit the "create a new route card" link on that page to get started.