May I make a somewhat different suggestion. I have just returned from a couple of weeks in Ireland where I enjoyed some of the best cycle touring I have ever had. Rather than bring my LHT I decided to take my BMC hardtail mtb, in the hope that as well as the luscious coast roads of Donegal, Clare and Waterford, I might find an interesting trail or two. I fitted a set of Conti Race KIngs mtb tyres, being light and fairly fast rolling and I found it all worked very well.
The larger volume tyres and suspension fork made for a comfortable ride, the seating position is more upright than most tourers and can cheaply be made even more so by adding an inexpensive stem and riser bars. The bike in question will also take road tyres, which will allow the bike to roll a little better should I decide to take that route. With a set of Crudcatcher fenders and a neoprene section between fork bridge and crown I stayed clean and dry even on wet roads.
The bike new, with all fittings cost about 550 UKP several years ago, so easily in budget. When I got back on my elderly steel framed Claud Butler tourer when I returned home, I was struck that a bike I have always thought of as very comfortable, suddenly seemed quite harsh.
The only downside is that, like any mtb, it will be distinctly slower than a more road focussed tourer. On the plus side, it has plenty of low gears for those big Donegal hills. Interestingly, when scientifically measured (on my bathroom scales) the BMC weighs about the same as my LHT.