Webserver Port

[Plantsman]

A change in ADSL Router has caused me a problem as I have only just discovered it doesn't support Port translation, but is a great improvement in all other respects. Previously to this my installation worked perfectly as I forwarded traffic on port 81 to port 80 on Zoneminder. I now need my Zoneminder installation to actually run on Port 81, not 80. I have changed the Apache conf file to listen on this port, and that all works fine and the text part of the webpages is returned, BUT pictures are not. I can't find anything in the zoneminder Options area to alter this behaviour. Can someone advise me which files within Zoneminder I need to tweak to get picture playback and realtime monitor viewing? The only option I've found that gives me some pictures is passing the cursor over peaks in the Timeline view, but these are static only and clicking on them or the peaks also doesn't work.

Many Thanks, Nick