Netonix Guys,
Final update..

As per my previous notes i have updated all the hardware at another site ( WS6 Mini's, UBNT AP's 7 UBNT NSM5 ) and have been monitoring the logs on the switches. Prior to the updates the logs were full of port state changes and following the updates i haven't had a single log entry on any of the switches.
Just for reference to anyone reading these notes... current version of UBNT kit is
UBNT Outdoor AP Plus - 3.7.39.6089
UBNT Unifi Controller - 5.4.11
UBNT NSM5 - 6.0 XW
Netonix WS6 Mini Switch - wispswitch-1.4.7rc8 ( & 1.4.2 )
The same applies to the initial site i was working on.
I am confident that the problem was generated due to one of the UBNT pieces of hardware ( personally i think it was the AP's as they were on a very old firmware version ) and since updating the firmware on those bits of kit the problem has gone away. I'm not so sure the firmware update on the switches has actually done anything as i have several switches at the original site that are still running 1.4.2 and there are no errors on those either. However... its always a good idea to keep firmware versions up to date hence why we went down that route
Thanks for the assistance and pointers, the use of shielded CAT5 inside the columns has been noted and the next run of cables purchased will indeed be shielded

.. after all.. i can't hurt.
Now all i need to is schedule updating the 200 or so other WS6 Mini's but i think I'll wait for the final version of the current RC firmware.
Cheers.. Rod