I'm so close to gold with 1:18:xxx on a DS3, and I can definatley improve cos when I did my fastest lap I was really slow 'off the line' and every lap I do against the ghost I'm always 1.5 seconds ahead going into 1st corner, but then I can't replicate my amazing 1st 2 corners and end up behind the ghost. I'm going to keep going until I nail it. I love these challenges.
The way I took the first corner is, turn in before applying the brake. This way rather than understeering you'll slide a bit. So turn, then brake.