Sorry for the late reply.
I DO appreciate all the help given to me by the forum members and apologise if my responses did not convey this.
Let me clarify a few issues:
The current ADSL/VDSL splitter is approximately 5 weeks old. It was replaced by a technician (at my own cost) together with the wiring when the issue first raised it's head. The cable is CAT6 directly from the splitter to the modem. The splitter is in the Demarc box where the line comes into the house and is attached to the Telecom phone cable.
All of this was done when Telecom advised me that if a tech came out and found nothing wrong withe line that I would be charged for the call out.
My actual distance to the cabinet is 550m and having now ruled out any wiring issues on my side, I can only deduce that the fault lies somewhere between the deamarc point outside and the cabinet or exchange.
Regarding my potential switch to VDSL, this was not done to poke Telecom in the eye but to appease my 3 kids( 2 teenagers) who are constantly wanting better speeds for the stuff that they do, Youtube etc. I also saw this as an opportunity to improve the speed and possibly sort any issues with the connection.
If my VDSL application fails, I will remain with Telecom as I have from the beginning. Perhaps it is time that Telecom looked at offering VDSL services to their customers.
My thanks goes to all those that responded and helped, plambrechtsen, sbiddle etc.
The story is however not over and I will keep all of you informed of my progress.
PS I did reboot the modem!