Sounds like the first descent is Warrens Hill road. In terms of Mendip, its one of the longer descents - the hills are only about 330m afterall, so you wont find really long descents anywhere.
Blackdown is a largish area. Assuming a literal description, the 'descent to the east' could be from the trig down to Burrington finger post.
Mendip is slippery and rocky - its the nature of the soils and geology - you won't find much in the way of trail centre type surfaces and you will have to work most of the trails to extract fun and flow. There are many and varied entirely off-piste routes and trails on the 'dips and the best thing to do is follow your nose, using the ROW network as a framework.
The best of the riding can be found between Sandford and Rickford to the north, Charterhouse to the East, down to Draycott and Cheddar to the south and Axbridge to the south west.
The weather is on the turn now, and so are the trails.