used to have their own language
that's right, like Wales and Ireland too. So the way English is spoken in those places, is like English words overlaid onto their old grammar systems....so you have eg different word order and constructions..that change English much more than accents do.
I am endlessly fascinated by this. In Welsh and Irish for example, there is no direct way of saying 'yes' or 'no'.. your answer has to agree with the question. Is Scottish the same?
"Are you going out?" "I am"
"Do you like sausages?" " I do"
This has obviously affected English too,with the endless 'question tags' that are such a nightmare for learners. .."isnt he?" " arent you?" Other more sensible languages like say Spanish, just have one question tag word "verdad?". No wonder so many learners have settled on 'isnt it' (innit) as a generalised question tag, which in turn, has affected the way English is spoken everyday,esp in London.
By the way I think OP's question should be changed to 'are you able to hear the different accents of English' - semantics,. semantics.