to keep this thread to a reasonable length, could we please refrain from posting line upon line of pings- the summary data from the end is much more useful. Some posted edited to make this thread a readable length.
To the OP-
It is most likely that this is due to the router being under a high load (which is quite likely for a core) and it is giving low priority to ICMP traffic- hence the sporadic results.
More useful analysis of the problem can be achieved by providing traceroutes to the servers you are trying to connect to, or even better than that some pathping data (have a google for a small prog to download). We will then be able to see much more clearly what is going on.
If you were to pass the ping stats you have provided to ntl they would just throw them straight back at you as you need much more proof of a problem.