Hmmmmm......if you dont know where you are going, or when you are getting there and still want to "get the best car deal" you have me nicely confused. Only by defining the first two items can one logically begin to define or refine the last item. Booking in all Irish cities will not work, because of yield management, you may not get a good price because of your guessed arrival time even if they honor your reservation at an earlier/later time of day.