It's exactly the same as buying from any other EU country.
First of all, VAT is 21% in �ire, so buy a car without the VAT. Make sure you get all the appropriate paperwork - and insurance to drive it!
You would then pay VAT in the UK - get an information pack from Customs and Excise on 02078653000.
You will need temporary registration plates - call DVLA on 01792772134 for information about all the forms you will need. Be sure to ask them if you will need to get a Certificate of Conformity from the dealer.
Youwill have to take the car to a Vehicle Registration Office and pay a fee to register it in the UK.
I am assuming you want to buy a new car. With the higher rates of VAT in �ire, the transport costs, the re- registration costs and so on, it is rarely worth buying a used car for import to UK.
Research before you do anything - car costs have fallen in the UK in real terms over the last few years, to bring the costs more in line with the rest of Europe. You could still get a bargain though.