Thought I 'd give you an update.
Fault has been repaired.
Luckily for me it had nothing to do with a possible delaminated fuse box, but more to do with my being a little careless. When trying to locate the relay(ECU) for wipers I had inadvertently removed relay responsible for indicators and replaced in in*the wrong socket. Hence, it shorted out left and right circuits. Presumably this is a relay socket for a legacy alarm system which was not used on my model because this function is incorporated in the alarm unit itself.
The wiper problem has not reappeared, however the contacts on the wiper motor have been cleaned and intermittent wipe is now working a lot smoother.
Thanks to all for assistance
Problem is fixed.