i'm in the fortunate positon that I need to pay some of the above taxes. My query is shoudl I approach revenue directly and lay all cards on the table, or shoudl i employ a tax advisor/consultant/ accountant to make my case?
You will need to complete a CAT return which is long and complex, it will cost you about from 500 euro up to get it completed by an accountant, well worth the money, there are lots of ins and outs with cat and reliefs that the revenue aren't going to tell you about, they don't do tax advice.