If you don't want the trouble of working it out and the profit is relatively small (my own guess under €6,000) and note you may miss the opportunity to save yourself some money just ring the 1890 PAYE number, give your PPS number and the amount of taxable rental income which would be Gross Rental Income less expenses (insurance, allowable interest paid on loans, repairs etc etc) less capital allowances (wear and tear on fittings).
That will take care of it through your tax credits, although it is a bit late in the year to be doing that for 2010. You should wait until early 2011 and ring them, and at the same time complete a form 12 for 2010. You may owe them some money for 2010.
The other option is to complete a form 11E and also to pay the tax (for 2010) before the end of October.