(G) Punto JTD ELF Starting problem when hot

Punto JTD ELF Starting problem when hot
Hi,
I am a newbie and this is my first post.
I have a Punto 1.9jtd Elf X reg. The car starts first time when cold however if it is run for approx 30mins then left to stand for about 30mins, it sometimes will not start.
I have read the posts similar to this and it seems to point to the RPM or CRANK sensor.
Does anyone know where this sensor is located. Pictures would be greatfully appreciated.

Regards Stephen.