The real challenge on Birmingham Long is the 2nd last corner for me. You come out of the sweeping chicane, and have to pick a braking point out of nothing, while turning towards a continually tight corner, aiming for a really, really late apex. It's piss easy to overtake the AI on it though, as anywhere on Birmingham.
A fun race is to stick it on 20x time acceleration, with a full grid, starting from the back - effectively a 24hr race in about 20min. See how far you can come up. If you don't make a easy, and actually have a decent AI ability that can match your times in the day, it's brilliant fun at night.