Basically to work out the daily rate you would charge you divide the old annual salary by 230 days (which allows for 21 days AL and 9 days Pub Holidays)...and that'll give you your new rate per day incorporating your compensation for annual leave and bank holidays.
You would also have to base the calculation on your last 12 months gross pay inclusive of benefits etc to make sure you are not losing out.
As a self employed contractor you lose your PAYE tax credit (€1800) but you can claim expenses against your income such as home office (light & heat etc), stationery, training, books, car costs, computer, broadband, etc
HTH