AFAIK, PAYE workers liability is satisfied by Deposit Interest Retention Tax (DIRT) which is deducted at source at the rate of 20% by the bank.
However, there was a discussion here before Xmas on whether or not Health Levy (2%) and PRSI (variable) needs to be paid. I'll try and root out a link later.
You are free to keep your UK bank account, buty you would of course be obliged to declare it to the (Irish) Revenue. The tax position would depend on the double tax agreement between the UK and Ireland. If UK DIRT is deducted I think that you are allowed a credit for tax paid against your Irish tax liability.
Although you are getting a 'higher' rate in the UK, is the advantage not eroded by the EUR/GBP exchange rate?