Was rather shocked to find BT hubs don’t allow you to change DNS servers anymore and force you to use their own ones, so I can’t properly setup adguard.
What routers are people using now that are reliable and will let me control my own network configuration
You should check if you can put your BT router in bridge mode.
This is typically how we used to configure these kinds of setups. This should allow the router you place incide the BT router to get your “outside” IP.
I don’t know if BT has any limitations on this, though, but it has worked with all ISP’s where I am located.