I think the lake district is all about the high mountain passes - try and do them all. It's not about speed, but as Sven says above, perfect GS territory and seriously steep.
+1 for the Campsite in Great Langdale, it's a beauty, you don't have to book, there are two cracking pubs nearby and the Wrynose pass is just round the Corner.
And don't miss Borrowdale - the loop around Derwentwater is stunning. And Honister pass over into Buttermere is a cracker too.