A bit behind as always… but struggling with this one for a while, so I felt it worthy of sharing the solution.
I got everything working on the LAN then setup port forwarding on my firewall for;
TCP Port 80
TCP Port 443
TCP Port 1494
TCP Port 1604
TCP Port 2598
Whilst I was able to access the storefront when I tried to launch my application i received an error;
Connection to the server "192.168.0.243" (the server's internal / private IP address) was interrupted. Please check your network connection and try again.
All the documentation and discussions online suggest that remote access is only possible using Netscaler, and although I may deploy Netscaler at a later date, for the moment I want to skip that step!
I found the default.ica file in C:\inetpub\wwwroot\Citrix\Store\App_Data contained an Address= entry (my installation uses mostly default values, and an excerpt looked something like this);
[ApplicationServers] Application= [Application] Address= TransportDriver=TCP/IP DoNotUseDefaultCSL=On BrowserProtocol=HTTPonTCP LocHttpBrowserAddress=! WinStationDriver=ICA 3.0 ProxyTimeout=30000 AutologonAllowed=ON
Simply adding my external IP address in the Address= section got me working!