"Local Area Network -Speed 100.0Mbps - Status Connected."
This is the speed across the local ethernet cable(s) connecting your system(s) to the router.
"Internet Connection - Speed 5.3Mbps -Status Connected"
This is the nominal speed your internet connection is running at.
"When I do a BT Health check on my Internet speed it shows around .450Mbps"
I have no idea what that is - are you sure it is .450Mbps (could it be 4.50Mbps - or could it be in MBps?)
Try this speed test - several times, and to different servers. click here