I have been testing on the new 28-03 skin with the new data.zip, for users using UK regional format of mph I have noticed the following;
If the_skin_Avicsync_by_pongo.zip contains the following folder media_libs with voice file code_advanced.lua in engine_1_0 and engine_1_1 then the over speed warning does not state the actual speed value it only says "The speed limit is miles".
If you delete media_libs folder from the skin and use the new data.zip the over speed warning states the correct speed value. for example if you were driving in the 20mph and you go over this limit, then the warning heard is "The speed limit is 20 miles".
I therefore conclude that this folder is not needed as we have a new data.zip which does all this now correctly.
I cannot say this the case for users using kph, perhaps someone can test this and report back.