You really must involve Lexus Ireland in this.That sort of service is simply unacceptable.
I would advise you to copy all future correspondence to both the dealer and Lexus.Try to get the name of of the MD of Lexus and address correspondence directly to him,ideally by your equivalent of Recorded Delivery post.Be firm,but fair, in your letters and document everything...dates,times, comments and conversations.That will kick the dealer into touch.
Good luck.