It's about 8 years since I last flew the A320, but I agree about the 230kt limit for the wipers.
Secondly, I don't believe that there is a QRH /ECAM for this as it is a pilot selectable item.
Thirdly, I can see nothing in the MEL (albeit not up to date) relating to dispatch restrictions.
To me, the crew on the day seem to have made a perfectly sensible decision, probably after consulting his Maintenance department, to discontinue the flight. I for one, wouldn't wish to test the reliability/endurance of a wiper motor for ~2hours on a dry screen.