I think I've found my issue? It seems that the SRX has a default COS setup. The problem is that I am linked at 1gbps but my bandwidth is only 15mbps, this is controlled downstream at the vendor router, so my SRX only knows it has a 1gbps connection to it's upstream router.
But when I applied it I got an error stating: Warning: 'per-unit-scheduler', 'hierarchical-scheduler', or 'shared scheduler' for this interface is required for bandwidth configuration on interface unit
I don't think I want a per-unit-scheduler as I'm not using Frame Relay or VLANs on this port.
Is there a simple something I am missing to finish this without setting up custom queues etc... I don't want to set any traffic prioritization or anything, I just want all my users to have a better internet browsing experience