Thank you both very much, I finally solved it.
Having configured virt-manager for use as a simple user I had a bit of trouble getting things right.
To recreate the default connection I had to use the command
virsh net-edit default (without sudo and using xml file provided by @ajgringo619 )
The new virbr0 connection in user mode didn’t connect, I had to open virt-manager as root and set it to autostart.
Now everything is finally working as it should!
Thanks again!