I am trying to find the birth and marriage details of Joseph Simpson born about 1815 in Cumberland. He married a Margaret(born perhaps in 1811, surname unknown)around 1835. Unfortunately the birthplace information for both of them changes each time on each census. Their first 5 children were born in Whitehaven,Cumberland, 4 more in Great Crosby,near Liverpool, Lancashire and the one in the middle,(my great grandmother, who subsequently married a Robert Chadwick) either in Cumberland or Liverpool! I have traced the grave for Joseph and Margaret, but cannot find their birthplaces, marriage details or parents due to their confused origins. Can anyone help me to get any further please?

It looks as though your biggest problem will be because National BMD Records only go back to 1837. However, it appears that, initially at least, you are trying to find the birth place of Joseph and Mary. Can we have some more clues?
What are the "different places" given?
In which census records have you found Joseph?
What year was their first child born?

I also have been confused by the different places of birth for the Simpsons. I believe Margaret's maiden name was Sharp. I can help with the marriage of Frances who married Robert Chadwick on 30th September 1863 at St Nicholas, Liverpool, Lancashire