SOLVED: This method was tested on a Nokia Lumia 720 but should work on ALL Lumias and possibly other Windows 8.0 Smart phones.
Basically I needed the last 8 digits of my sim card number to register to manage my mobile online. Unfortunately I had cut my sim due to a phone change and the numbers did not show. I had also lost the original sim card holder that contained the number. Therefore I was at a loss and needed another way of retrieving my simcard number.
After a bit of playing with my phone I found out how to find it via the Nokia Lumia, here follows the step by step guide.