Maintenance

Hi. I was wondering if anyone could advise me in relation to a maintenance issue. I have been separated from my ex for 12 years and our first issue in relation to maintenance came in 2009. I took him to court in Dec 2009 for arrears of €2100 and other issues in relation to his loss of interest in our daughter. It was more important to me he repair his relationship with our daughter and picked up with the maintenance so I let the arrears go because I didn't want him to be angry at me. (In hindsight I regret being foolish).
So the relationship did not improve and now my daughter is 15 and feels no connection with her Dad. A year would go by and she wouldn't hear from him.
Recently, I have had to go back to court for €2800 arrears. Our court date was set for Jan 15th, and he did not appear, instead wrote a letter to the judge saying he couldn't make it as he was at a wedding. A rescheduled date was made for the following week. Two days before that date he called me (which he hasn't done in years) and offered me a reduced weekly amount (€20 less), and his reason for this was that he was struggling and his work situation was unpredictable. I took his word for it and empathised, as I too am struggling financially and I am out of work for the first time in my life.
We went to court anyway and I agreed to this (He had a solicitor, I didn't), he offered €500 lump sum off the arrears and €10 per week off the remainder of the balance.
I wasn't over the moon with this but accepted it and decided to move on.

About a week later my daughter let slip, that her dad, his partner and their young daughter had recently been in Spain for a weeks holiday but we are unsure whether it was the first or second week in January.

I feel extremely annoyed about this and if I had've known this prior to our court date, I would've hired a solicitor and not agreed to the reduction in maintenance or the arrangement to clear the arrears.

He does not contribute to any other expenses in relation to our daughter's school fee's, medical, Christmas and shows no interest for her welfare at all.

I am really struggling financially and I feel completely stressed to have found this out. I know that he has a very good social life and had been to a wedding and other large parties are planned for his family, but I feel he consciously chose to spend this money (he claimed he hadn't got), on a holiday in January and let his daughter go without for 7 months.

I have been in touch with a solicitor to see if my decision can be reversed (I wouldn't ususally rebel, have turned a blind eye too many times over the years to save myself from dealing with conflict) - I feel I can't let this go!
I'm hoping someone can help me along with making a decision about whether or not I should fight this.
Thanks.