It turns out it was the CentOS firewall blocking the connection - not Windows or Hyper-V.
In case anyone else has the same issue you need to edit the file /etc/firewalld/zones/public.xml and add the lines in red below to open port 9091 to local addresses 192.168.1.* and then reload the firewall with firewall-cmd --reload
You can then access the service through browsers on your LAN. Hope this may help someone
<?xml version="1.0" encoding="utf-8"?>
<description>For use in public areas. You do not trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.</description>
<port protocol="tcp" port="9091"/>