Another site that has the options of OSM based routing as well as Google's and of displaying OS maps is gpxeditor.co.uk
The interface is bit "special". It's all done on "context-sensitive" menus (that's right-click to you & me).
Certain aspects are rather audax specific (km only, not miles for instance)
It's been developed by a member over on YACF
Some of us might remember him on here too, took himself a bit seriously ....
Not THE 'serious cyclist'?