Yeah I guess it's too new-fangled to have it's own page on TMA. As you say, I reckon the builders incorporated whichever older places looked useful though. so there are links to the Wansdyke page on tma here and there.
I like Maes Knoll
http://www.themodernantiquarian.com/site/2882/maes_knoll.html
and its weird 'tump' which they say is part of Wansdyke (but seems a very useful thing for a hillfort to have).