I upgraded to M500 on the 27th of August the adviser at the end of the phone told me it would take effect immediately. But I am still only getting around 230. I have contacted support who have run tests and told me to reset router which I have done numerous times now by this point but no change in speed.
What device are you measuring speed on, and is that wireless or ethernet cable connected?
Some mid range or budget wifi devices will top out at around 230 Mbps over wifi in real world conditions. You may also want to check that in the Hub's advanced settings, the 5 GHz channel width is set to 20/40/80.