Have had the opportunity to pock around our newly acquired 200TDi.
It doesn't have a CCU; although the 300TDi does according to my Haynes Book of Lies - sorry..."manual" - got no idea if the 300TDi's CCU controls the various functions on the wipers though.
Now - presuming you have a 200TDi or pre 95 V8...
Looking at the wiring diagrams in the Haynes manual I can see there is a "Park Switch" in the motor itself (presumably controlling the position of the wipers when parked by means of a switch that is activated by some kind of cam or lever?).
There is also a solenoid and resistor/switch asembly in the front wiper relay. Maybe that somehow acts like a capacitor discharge unit to give intermittent wipe...I'd guess the "capacitor" holds enough juice to open the relay (thus energising the wiper motor) for one sweep of the wipers; the more slowly the capacitor is charged up via the resistor, the longer the delay?
I'd suggest that you should try substituting a know good relay and see if that solves the intermittent wiper issue. Also have a look at the motor mechanism and see if you can work out how the "Park Switch" works...might just need some WD40 if you're really lucky!! The microswitch controlling the stop position on my first Rover 800's sunroof was fine after a burst of WD40...
Sorry - not the most affirmative response and theres a fair bit of guesswork in my response, but in the absence of anyone else knowing an answer I hope that points you in the right direction (or at least towards a solution!).
Obviously if you find an answer that doesn't involve replacing expensive components wholesale...post it up here please!!
Malcolm