I'm not entirely sure I understand, but some thoughts.
The kilt in the UK is thought of as Scottish, not English or Welsh or Cornish or Manx or even Irish ( although there are kilts for all parts of those regions)so I'd be surprised at it being thought of as British. I grew up in Northern Ireland and they were very rare things, we knew about them , but only thought of them a Scottish, and actually not even all of Scotland but more of the Highlands.
I confess to being a little bemused that other nations have taken the kilt onboard as in some sense part of their history or culture, but jsut to be clear, I'm in no way against anyone wearing a kilt, it sometimes seem a little odd to be known as "pan celtic" when historically it was only ever seen in a very small part of a small country.