Trailforks is volunteer based information and some of it is fed from Strava. I wouldn’t rely on the grading on there. A hard core DHer will mark something they think as tame as blue and yet may be more of a red or black style trail centre trail. Not that it’s a trail centre at all.
Rough, changeable trails with conditions and whatever digging has been going on. Week to week you have to be watching out for changes. Except for the only official trails… BKB, Yoghurt Pots and Summer Lightning.
Currently conditions are messy outside of the official trails. Holmbury hill is perhaps the one that holds up better. Pitch and Winterfold has some of the more fun bits and proper steep stuff around, though very short. Some trails around Winterfold shown on Trailforks you may find are gone.
Leith… there’s loads of hidden gems, but you need to link it all up. There’s way more than just Summer Lightning and the jumps just north of the tower. Many good bits are a bit cheeky though.
Redlands… rule of Redlands is we don’t talk about Redlands.
There’s a lot more to Surrey Hills beyond these areas. Another area beginning with R but we don’t talk about that either 😉 , likewise things somewhere near Box Hill. Though anything on the North Downs side is v.slippery chalk when wet.