If your employer pays as salary, they have to pay PRSI on the additional amount.
If you redirect this additional income into your pension, you have to pay PRSI and USC on the contribution, something you are not charged if it is paid directly by the company.
It's cheaper for both of you for them to pay into a pension plan for you.
Are they setting up an Irish bank account, registering with the Revenue etc? If so, it won't be a problem setting up a pension. If paying you from the UK, not all insurance companies will accept payments from outside Ireland.
Steven
http://www.bluewaterfp.ie (www.bluewaterfp.ie)