You can obtain your sync speed from your IP profile. To get your IP profile, go to http://speedtest.btwholesale.com/ and run the speed test, then click on the Further Diagnostics button. Multiply the IP profile by 1.033 to get your sync speed. The 78Mb can be ignored, this is just Plusnet's default maximum speed. The upstream sync will be 20Mbps.
You cannot obtain the sync speed from the router, you can from the modem, if it's an HG612 and if you unlock it.