Invalid DNS on Virgin Media Hub 3

My machine drops the internet and returns an invalid DNS.

Running Mac OSX 10.14.1 on a MacBook Pro and a MacBook Air with a Virgin Media Hub 3 as a router.

Problem appears to be random.

When I connect to the network successfully I get a DNS of 194.168.4.100 194.168.100

When the internet drops the DNS shows 10.0.1.1

Sometimes I cannot reconnect to the internet for several hours. The Wifi link to the router is successful but with a DNS of 10.0.1.1 I cannot reach any sites! Eventually connection is successful and here I am using the web.

So to help understand this can you help me understand where the DNS is generated (on my Mac, in the router, downstream at the ISP)?

Currently I have

Configure IPv4: Using DHCP

Configure IPv6: Automatically

As I know the valid DNS for this ISP could I go "manual" and enter the correct address in the DNS tab of Network Preferences?

Any advice welcome as this is extremely frustrating.