"'Paradoxically,' A.J. Aitken reports in OCELang. (1992), 'for working-class Scots the common form has long been Scotch ... and the native form Scots is sometimes regarded as an Anglicized affectation.' ... Outside Scotland...Scottish preferences are less well-known. Scotch is likely to occur, both as adj. and noun, in contexts which middle-class Scots would regard as either droll or improper."
The New Fowler's Modern English Usage, Third Edition, ed. R.W. Burchfield, entry "Scotch, Scots, Scottish"
My usage has precedence both within Scotland, and more generally within the U.K., while it may be jeered at by fancy lads or pommies.