To all who have replied,
Thank you very much for your replied, much appreciated.
I went to my local Ford dealership this morning to see if i can find out any additional information:
The technicians informed me that unfortunately the white gunk if used writes off the tyre.
The local AA mechanic was there at the time of my visit, and he too confirmed this, apparently its due to the chemicals in the gunk which has a detrimental effect on the rubber inside the tyre. He recommended using Green Slime, apparently its water based and was sold by Halfords. He did say that there were some tyre centres who would still not repair your tyre after using this.
Both Technician and AA mechanic advised using your breakdown service, as most repairs can be plugged at the roadside, which will enable you to get to a tyre centre and have your tyre repaired. (Obviously, that if its repairable)
Hope this is helpful………