Jarvella (2001) is interesting; [apologies for the exclusivity of academic publishing if you don't have an Athens account, dear reader]. The essential point for my current research is that 74% of the time, Danish Anglophones (unfortunately we do not know their level of English) were able to distinguish between English (northern and midlands), Irish, Scots and American speakers' accents.
RP was excluded from this study, but Ladegaard (1998a), dealt with it. (Ladegaard was clearly on a roll in 1998: Ladegaard (1998b) is on a similar theme, and appears to be open access.)
The point, from the CDA of listening materials aspect, is that accent is conveyed to learners.
I need to go away now and read the two Ladegaards.
Jarvella, R.J, Bang, E., Jakobsen, A.L., Mees, I.M., (2001) Of mouths and men: non-native listeners' identification and evaluation of varieties of English. International Journal of Applied Linguistics Vol 11 No 37 - 56
Ladegaard, H.J. (1998a) National stereotypes and language attitudes: the perception of British, American and Australian language and culture in Denmark. Language and Communication. 18: 251-274
Ladegaard H.J., (1998b) Assessing National Stereotypes in Language Attitude Studies: The Case of Class-consciousness in Denmark. Journal of Multilingual and Multicultural Development Vol. 19, No. 3, 1998