I would think very carefully about this, not meaning to put a downer on your plans, but you need to think about why you want to move.
Is this a temporary or permanent move? If only temporary, finish the exams here or do the irish exams abroad. If permanent then do them in the UK. That said I'm not sure how easy it will be to transfer. There are more issues here than just accounting and auditing standards. Most small/medium businesses and firms of accountants will expect you to be able to deal with tax issues as well as accounting issues. The transition is not as easy as one would think.
To explain, I did my degree in University of Limerick in 96 and moved to Uk where i sat and got my exams, I qualified in 2001 having started from scratch, no exemptions available as degree work Irish related not Uk. I then moved back to IReland in 2005 Feb, to work in small practice in Portlaoise, I must admit it was a steep learning curve. as a qualified accountant, with little or no tax knowledge. I was there six months and was 'let go' a six month contract. I spent from Sept until Jan looking for work in Ireland. I admit i am now working and think i have a handle on things tax wise etc, but still struggle at times.
On your own issue, I cant really see the difference other than its the other way around. I also have Irish institute membership, great you say, but for rest of working life, have to pay membership to both UK and Ireland.
Think hard about long term plans, and good luck with the decision
PS are there not jobs available to relocate to carribean or other places for a 6/12 month contract, etc from Ireland, these were always being advertised in Uk