I think I am in the closing phase, I however don’t see where a customer will be able to post a job on our site for suppliers to see, how can this be done please?

To allow your website members/visitors to post jobs, the best option I would say is to use the Classifieds app for that.  That should work great for you.

Here is the User Manual Classifieds App section: http://www.ultimatewb.com/classifieds-app