I have to admit that, like Jock, District tartans were complete strangers to me before I joined here. The first non-clan tartan I ever came across was when a work colleague who was in the Tartan Army bought himself an ex-hire "Flower of Scotland" kilt. His choice was dictated by what the shop had that would fit him and he never considered his clan for a moment.
It is nice that there are tartans available nowadays to fit every eventuality but, as Jock says, they are a total irrelevance to us Scots people - yet another fact like Borders families never having been clans and Irish people never having worn kilts that seems to cause immense difficulty here and raise recriminations against the person who has the gall to even hint at it.