PROBLEM SOLVED!
For anyone who comes across the same problem the resolution was;
If your CCTV kit's output resolution is set to a resolution where it should be classed as a computer signal - and have a refresh rate of 60Hz - but when monitoring the cameras then the kit is sending out 50Hz then the TV won't accept that as a valid combination. IOW, the TV accepts say 1280 x 1024 @ 60Hz, but not 1280 x 1024 @ 50Hz.
The answer is to use a HDTV timing where both refresh rates are valid. So, 720 x 576p @ 50/60Hz, or 1280 x 720p @ 50/60Hz, or 1920 x 1080i @ 50/60Hz, or 1920 x 1080p @ 50/60Hz.
Read more: http://www.diynot.com/forums/audio-visual/cctv-setup-problem.394788/#ixzz3VQxAn96t
taken from this post;
http://www.diynot.com/forums/audio-visual/cctv-setup-problem.394788/
Cheers.