Pegeout 206 1.6 8v 2000 - Erratic idle/reving, starting problems - Mookwalker

Hi,

Pegeout 206 1.6 8v 2000 model. My car is driving me crazy! Won't start when hot, starts when cold. Also, reving erratically (around 3k revs)usually when driving and dip the clutch to change gear the revs do not drop. Just now I was stuck at a junction in neutral and it was stuck at 4k revs. Normally idles at 1k no problem when cold. Any advise welcome? I am thinking Crank sensor?