If the loan is with a British bank what you can do is transfer from your bank in Ireland to the U.K. bank
You will need the UK Banks IBAN number, The BIC/Swift number, Bank Branch Address, Loan Account Number. ( These should be on the top of any statement you have from the UK)
The transfer may cost you 10 Euro depending on what bank you are with.
I had to do this recently and the Irish Bank Clerk could not tell me the exact exchange rate I would get as the rate applicable is the one current when the funds reach the U.K. account. The Bank will tell you that this will take 4/5 working days but usually the electronic transfer is done within 24 hours.
With the exchange rate as it is now there is not a better time to pay off UK loans ( Of course Sterling could continue to deteriorate against the Euro but thats the gamble you take)