Those will get you started. The guy who wrote the STW article is actually a riding mate of mine.
The main concentration of trails is up around Black Down/Rowberrow/Burrington Combe. All the bridleways on the OS map are rideable and there's a network of unofficial DH trails in the Rowberrow plantation woods.
Down the east rim of the gorge by Jacobs Tower is a lovely descent - fast swoopy bits interspersed with jagged rock gardens, best done early/late in the day when there aren't so many tourists wandering around!
Badass bikes is well worth dropping in, the guys there are pretty switched on. Box (Rob Cooksley) who runs it is an ex DH and enduro racer and all round top bloke.