Many years ago when I lived and worked in the west country, there was an incident where my rather tough boss Richard was giving someone a jolly good dressing down on the phone. As he put the phone down, he muttered the C word which was unexpected considering the admonishement itself had been bereft of expletives.
I cracked up, Richard cracked up and Denise our well spoken secretary who was in an adjoining office with the door open shouted through "what's got you boys laughing"
"Richard just called (whoever it had been) a word that rhymes with a flat bottomed boat that goes down the river" I replied. There was a long silence and she came back with "I can't think of a swear word that rhymes with gondola"
Took us well over an hour to recover.
As for Denise and her posh accent, it was all well and good most of the time, but if she got excited and wanted to labour a point she'd say in the broadest west country Dunnit evurrr.