Hi,
Issue resolved.
Passive mode on the FTP had to be setup, this is quite confusing as it had already been tested (I believe :) ), I guess it was one of those situations I was too impatient and making too many changes I never properly tested. Feel a bit silly since it was right in from of me and a quick good search shows 425 is related to access issue.
Tip for anyone who has a server on a routed connection (basically you are behind edge device with a completely different IP than yours) you will need to setup passive mode. A quick port check can be done by the FTP response for the passive mode, example; 227 Entering Passive Mode (176,31,106,184,255,231) take the second last number and * it by 256 then add the last number, so 255*256+231 = port 65511 - so this will give you a clue to what ports are attempting to be used.
For my issue, I was seeing ports all over the place so I had to manually set the specific ports under the Passive Settings and then setup an Inbound rule on the firewall to my server IP.
Regards
Robbo