As Professor Joad used to say, "It all depends what you mean by ....".

In, say, "The Maid Gaed to the Mill" I deliberately change it from Scottish to English to make it suitable for me to sing, but in Les Barker's parody "Belle's Bonnie Bogie" the overdone "Scotch" accent is a large part of the song, so I really ham it up - the more over the top the better. (Although I think my fake Scottish accent is quite convincing, I don't know what a Scot would make of it)

WassaiL! V