Thanks for the comments folks.
Willie:
The fluid seems to 'osmisisize'

through the wall over its entire length, and fluid takes a few days to build into globules if the car is not used, but the pipe dries quickly (in places) when the car is driven and thus would possibly appear to be OK to the daily driver.
I may have been inclined to dismiss this as condensation or something like that, had it not been for the loss of rigidity of the pipe itself...and the fact the residue IS brake fluid
Anyway, I don't want to be alarmist, but please keep a check on your installation if you have one fitted.
I myself am going to replace my entire kit with a copper piped system that only costs (new) £12 more than one I have now, and return my latter to the supplier for a full refund. I'm not risking anything with my brakes!!
P.S. I renamed the post to attract attention to this observation.