Thank you. The factory reset worked while the computer was plugged straight into the Virgin hub. But when I put it back into modem mode the speeds dropped again.
The odd thing is I had faster download speeds before the upgrade to M500 and I haven't changed anything on the virgin hub or my router, so I don't understand why the download speed has dropped once it has more 'available'.
Same computer, switch, wiring, etc before and after. All gigabit enabled.