Unless you start to increase your mileage son and ride with weight on your bike, you will find it harder than you need to. I know because the first stage of my attempt at an around the world bike ride was from Surrey to southern Ireland (Cork) and those first few weeks were exceptionally tough physically and mentally and there were several days in south east Ireland where I seriously doubted I could do it.
We simply had not done enough in the way of preparation.
80km a day is a sensible target with 1 day off a week. Your body needs time to heal and repair and it is useful to rest, write things up, eat and general check kit over on the 'rest' day.
Also you will need to factor in the ferry to Rosslaire which will mean a much shorter mileage day. If you need the name of a really good b&b just outside of rosslaire let me know, we have friends there and they are exceptionally accommodating and whilst a few miles off the main road it is lovely and quiet and you will get plenty of sleep.