Because Ireland is a simple hop over the sea from the English coastline, many people choose to commute weekly between the two. In response to this, airlines offer multiple opportunities for business people to make the short journey, and flights tend to be relatively cheap.
There are certain times, however, during which prices sky-rocket. Over Christmas, for example, airfares increase astronomically and those who choose to work in London and live predominantly in Ireland, are stuck facing seriously expensive travel costs.
In order to avoid this unfortunate seasonal hike and secure the cheapest flights available, it is important to plan your life in advance. Well before Christmas or Easter, take some time to glance at your work and home schedule.
If you can, sketch out the periods of time during which you will be in Ireland and those during which you will be required to be in the UK. Once you have determined your personal movements for this time, check these against flight schedules. Most airlines will allow you to book tickets up to a year in advance, and these will be significantly easier on your wallet than any you secure during a holiday season.
In short, then, avoiding the steep price hike which afflicts the air travel industry during holiday seasons, is a matter of planning. Simply put, you need to make sure you have organised your movements during the festive months well in advance.

