Wait until you return to Ireland to set up the Irish Ltd company.
If you as director of the Irish company and are resident in the UK, you could make the Irish resident company resident in the UK, and liable to UK (and Irish) Corporation tax. This should be avioded if possible.
Put your UK contracts through the UK company, and Irish contracts through the Irish company in due course.
This should keep matters simple.
One other point - what are you going to do with the UK company on your return to Ireland? How many directors? Take professional advice re sorting this out, as being Irish resident you could make the UK company Irish resident also, and liable to Irish Corporation tax.