Sentence:  While there are some Cockney elements observable in northern English (such as /t/ fronting), other regions of Britain have manifested their own <WSD>casualisations</WSD> of RP towards the local vernaculars. So people talk of 'posh Geordie', 'posh Brummy', 'posh Scouse', 'posh Yorkshire Leeds' and so on ... 
Meaning of the word marked with <WSD> tags:  The process of making anything casual.