Yes that's correct. You booked a non refundable ticket (save for some taxes) using cash and avios (the avios here essentially acting as a discount to the cash price). It acts the same as if you bought the ticket normally all cash i.e. also not refundable on saver fares.

Avios reward tickets which are purchased through a dedicated page and via the avios group are different. They are refundable (minus a fee of €42.50 which is usually deducted from the taxes and fees you would have paid).

Possibly a harsh lesson for you here which Aer Lingus are happy for most people to fall into. You should nearly always try to redeem your avios for flights using a reward flight first, the cash and avios option is really only useful for people who collect avios infrequently and have small amounts.