I am a PAYE worker, with small rental income for the past 5 years. I have always completed a form 12, and have never had any problems with this. I don't know why they are looking for a form 11. The covering page of the Form 12 states who it is applicable to. It seems to me that you fall into this category, as you do not have gross income outside of your PAYE inome of 50,000 Euro ot more.
I'n no expert though - just an ordinary citizen......... so you may need to get professional advice.