I finally got my new bike. It's a La Pierre RCR100, I got it in the cycle superstore in Tallaght. I've cycled home from Tallaght and then to and from work yesterday and it is amazing the difference a road bike makes to the journey.
I've done both trips on my mountain bike and it is quite hard work but on the new bike it just flew and I've done both journey's in record time.
If only there was a cycle lane all the way to the city centre like there is to Tallaght!