Hello and Welcome..
My name is MIKE - IM happy to help you.
The crank sensor on your Hdi engine is indeed very difficult to see let alone get at -
It is located on the gearbox bell housing - about where it abutts the engine -
you need to remove all the air tubing etc - to gain access to it - so basically you are aiming to get access to the top of the gearbox - and you will then see it there.
Do let me know if you need anything else at all - Kind Rgds - MIKE....Meantime..............Please do click on the "OK/ Excellent ratings" for me as that's how Im credited for helping you - Thank you in advance for that...You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..Rgds, MIKE.