Ok, so this is solved. Turns out, ofcourse, I made a stupid error.
When using NAT, i'm making the guest machine available over 127.0.0.1 and using port forwarding in the VirtualBox NAT networking settings. Forwarding port 30303 - the port my docker nodes are using- basically occupies this port on my local machine. As I also ran my windows node on this port, discovery would never work. (addPeer still works though)
I switched my local node to run on a different port and it worked immediatly...
I haven't found a good guide for this on the web, so I'll try to make this answer be one

How to setup eth-netstats and eth-net-intelligence-api
Installation
You need something to run a local blockchain (Ganache is great)
Install the beautifully named eth-net-intelligence-api (it sits between the chain & eth-netstats)
(also need to install pm2 for running eth-net-intelligence-api)
Install eth-netstats (the actual lovely web interface to the chain data)
Configuration
There actually is very little configuration required to get this started
In eth-net-intelligence-api
edit the app.json
file :
[ {
"name" : "aName",
"script" : "app.js",
"log_date_format" : "YYYY-MM-DD HH:mm Z",
"merge_logs" : false,
"watch" : false,
"max_restarts" : 10,
"exec_interpreter" : "node",
"exec_mode" : "fork_mode",
"env":
{
"NODE_ENV" : "production",
"RPC_HOST" : "localhost",
"RPC_PORT" : "7545",
"LISTENING_PORT" : "30303",
"INSTANCE_NAME" : "anInstanceNameIsRequired",
"CONTACT_DETAILS" : "",
"WS_SERVER" : "http://localhost:3000",
"WS_SECRET" : "aSecret",
"VERBOSITY" : 2
} } ]
Note :
the RPC_PORT
changed to 7545 for my Ganache chain
the WS_SECRET
value is needed below
To run
1) Start your chain (with Ganache this is a GUI)
2) eth-net-intelligence-api
pm2 start app.json
3) eth-netstats
WS_SECRET=aSecret npm start
4) Go to http://localhost:3000
Best Answer
Setup nginx as proxy server for your node below script for your reference