Not 100% sure of the current situation around rolling over gains from UK to here, but pretty sure that you cannot do it. As the previous poster suggested though, get good independent advice. This is more difficult than it sounds, most Irish accountancy firms have to sublet the UK business to contacts in that territory.
Finding a company that knows not only the tax code in both countries, but also how the taxes affect cross-border transactions, is not easy. You won't get any help from the Irish or UK tax authorities either, they don't know (and don't really care) about the dynamic of dealing between both countries. Each one worries about their own jurisdiction, but knows little or nothing about a situation like this.
What I do know is that you only pay CGT at the Irish rate of 20% (in Ireland) and not at the UK rate.