TechBear, speaking of the late nineteenth century:
It was at this time, as part of these nationalist movements, that the Irish kilt and Welsh cilt first made their appearance, as well as the introduction of Irish tartans.
Regarding Irish tartans, the earliest we can find any solid evidence of the creation and use of Irish tartans is in the 1960s and 1970s (and then largely in either Scotland or North America, not in Ireland itself). The exception to this would be the Ulster tartan, which is an artifact tartan discovered in 1956 (and which may have been the inspiration for the design of other Irish tartans). The Irish county tartans that are so popular today, of course, were designed in the mid-1990s. All this is to say that the Irish tartan phenomenon cannot really be traced back to the late nineteenth century.

And regarding Welsh kilts, I daresay kilt wearing among the Welsh is something one has seen more of in the past few years than ever before. The very first Welsh tartan was designed in 1967 (the Welsh National). Before that, I don't think there really is much evidence for the Welsh using the kilt as part of any nationalist movement.

Regarding Welsh tartans, McClef writes:
It's difficult to find evidence of it before the 1970s when the most famous Welsh tartan was designed - the Brithwe Dewi Sant.
This tartan was actually designed in 2002 by Sheila Daniels for the Welsh Tartan Centre in Cardiff -- the same company responsible for the recent design of all the Welsh family tartans. Maybe you are confusing this tartan with the Welsh National designed in 1967 I mentioned above?

Lastly, Phil writes:
In Scotland kilts were not worn as daily attire and still are not to this day
I assume you are referring to the late nineteenth century specifically, but as you did not give a time frame for the above statement in your post, it could be read as an assertation that the kilt was never worn as daily attire and was always conceived of as more ceremonial dress. Certainly by the end of the nineteenth century it had become ceremonial dress for the great majority of Highland kilt wearers, but it's origins are, of course, as an every day garment. I just didn't want anyone to misread the above and get the wrong idea.

Aye,
Matt