I can't say I've ever hear it in the south west, but in the west midlands (specifically black country area) the 'am' replacing 'are' is a very common construct (possibly because 'ar' is used in the same context as 'aye' so "Oh ar" or even just "ar" = "Oh aye!" in other regions) so you get things like "am ya?" = "are you?" and "you'm" (or even just "yam") being a contraction of "you am". anecdata: when i lived in Kidderminster, my more well spoken friends used to call people from Stourbridge "Yam yams" because of their propensity to say "Yam awrite am ya?" (Are you alright?) as a greeting