Best way to monitor bandwidth usage?

[bazaarboy]

we have 4G broadband with a limited data allowance, though you can buy more gigs when needed

Recently our data usage has gone up and I'd like to monitor and pinpoint which device(s) are responsible

We have 4 pcs, 3 phones, tablets and multiple connected devices like sonos, home automation hubs etc, so it's difficult to be sure who or what is siphoning the data

Can anyone recommend an app / windows program to help break down usage??
Thanks!

 

[bazaarboy]

The higher data usage has coincided with a new media server, which runs 24-7 and yes, it's win10.

I was wondering if I can monitor the data flow through my draytek router, which in itself has limited options for global continuous monitoring