score:4
The transit planner can only be as good as the information it gets from transport companies so the answer to your question seems to be, no there is not a reliable planner. I looked at http://www.traveline.info/ and got the same false information you did. You could try the national express site on this occasion http://www.nationalexpress.com/help-and-advice/tickets/about-our-timetables.aspx
Upvote:5
From my experience using http://www.traveline.info/ the information has always been up-to-date and to my knowledge is the only UK site to integrate bus, coach and train timetables and to offer itineraries using mixed modes of transport if appropriate.
Obviously always worth double checking with actual bus/coach/train companies own websites, where traveline can be the starting point to find out who the companies are that operate a given route.