Last time I worked in Ireland was around 2006 so I dont know what the rates are now since the downturn. Yes there is work in the UK for Carpenters and Joiners. All the guys I know are working at the moment.
Wages depend on where you are and whether you work PAYE or as a sub contractor which is easy to do here as most people are self employed in construction.
Wages/ rates are tricky becuase there is a lot of agencies here and they pay low rates compared to say you working directly for a contractor.
Working directly is anything from 15 to 20 euros an hour approx. This varies a lot as you can imagine, I work on and off for several contractors along with doing my own work. I try and avoid big site agency work but a lot of guys I know love it because of the price work. They can make substantial money on price but it can be intermittent.
I find everyone can negotiate their own rate, and it largely depends on tools transport and experience. Agencies will charge the contractor about 18 -19 sterling and hour but pay the carpenter about 12-14 on average. This may well vary from region to region. London seems to have its own economy and set of rules! I would imagine you could get great money there but rents and cost of living would counter it.