disgraceful behaviour but not unexpected from AF who own Cityjet.
Your ticket price suggests that you bought a ticket in K class which is refundable if cnx before departure and incurs only a fifty euro fee if cnx after departure. You may have those details on your print-out. However, that's academic because your flight was cancelled and thus you were entitled to a full refund.
I do hope you have proof of everything - the print-out of the "ticket", proof of cancellation etc etc. And be ready to put your complaint in writing.
Look at the aviationreg.ie website for rules regarding your entitlement - and phone them -numbers on the site. They are - as their name implies -the body that enforces aviation regulations.
Also, there is an Air France rep in Dublin whose number was, and may still be,6050383
(i don't think many people who post on the travel section of this website have paid -out of their own money- €450 for a flight to London !)