ballymun flats?

Yup, it sure was.

does anybody know if ballymun towers were demolished? has that part of dublin changed a lot since the movie was filmed?

Yes, indeed! My father-in-law was a shop steward of the Seven Towers, a fact he detested because he believed no one should have to live in such wretched buildings--that people shouldn't have to sell their souls for an indoor loo. And he was so right! At the time of construction, there was still plenty, of good, cheap land for cottages, semi-d's, and row houses--all with gardens and a dry shed for turf, logs, coal. The government had to a few thousand poor out of the city centre--those so-called gurriers were such an embarassment, and Ireland was "going places! The gov't also wanted to "settle" as many Tinker's as possible for reasons that are to complex to deal with here--besides, many of those reasons are in the film.

The towers are gone now, and while their are lovely homes available, you won't find more than a handful of the former residents of the Towers living in them since they were built for profit. The undesirables, the poor, the infirm, and the elderly have been relocated "elsewhere", and the "undesirables" who were sent to places like Limerick, Listowel, Bantry, etc., have created literal warzones wherever they land. And by the way, there are still plenty of people--mostly single mothers--who live in such Dickensian squalor that our entire nation should be ashamed to call itself "developed". Obviously, unethical bankers are far more important to Ireland's future than her children are.