I used a couple of airline sites - Kayak and Which Budget to see what are your options. Whichbudget only lists one low-cost carrier to Rabat. It is via Paris. From Ireland, the only discount flights going to Morocco were to a city farther in the South - Agadir. I suspect your best bet may be to go via Paris. There may also be an option going via Spain. Or maybe even to go via Casablanca. You may be able to get a driver from Casablanca to Rabat.
I'm also hoping that you may be able to get some suggestions on what to see from our members.
I've been to Rabat. We flew into Casablanca (from the New York) on Royal Air Maroc, rented a car and easily drove to Rabat.
We went to Rabat only because, at the time, I was an Arabian horse breeder and had an invitation to visit the king's stables.
From Rabat, we drove a loop through Midelt, Fez, Volubilis, etc. ... through the pre-Sahara and back up to Marrakech. We spent a few days in each village and then a week in Marrakech. We spent the last night in Casablanca for the return trip home.
That was awhile back, so I don't have any recent info to provide.
That said, I've been mentioning Morocco to my husband a lot lately! I'd love to visit again.
