Changed router ip accidently. Can’t change it back

I've done this successfully. You need to move your machines from 192.168.1.* into the 192.168.0.* subnet. If they are all on DHCP you can reboot, but it is a lot quicker and easier on Windows to use the connection repair function, or from CMD:

ipconfig [/all]                # to identify the interface name
ipconfig {interface} /release  # to clear the current IP address
ipconfig {interface} /renew    # to assign a new IP address from DHCP
ipconfig [/all]                # to check the new IP

On Ubuntu, you can simply disconnect and reconnect the interface.

If the interface has been set manually, you will need to change the assigned IP and gateway within the interface's TCP/IP properties.

Once a machine is in the new subnet you can then access the router again through 192.168.0.254.

It should take only a couple of minutes.

Eventually, it was a VLAN Misconfiguration with VMware - I'v reset the VMware virtual network/s to default, and the problem has resolved from itself.