Turner and Ireland in Cork

My ancestor Mary Turner was born in Cork in around 1807. On 3rd July 1821 she married William Ireland at St Finbarr's. Yes I know that would make her only 14! Maybe she was actually a little older but fudged her age on the census. By 1828 they have emigrated to London, where their  6 children are baptised in the Sardinian Chapel. By 1841 William is dead and Mary remarries in London to my ancestor John Pearce. They have 2 children, Richard and Ann. Ann is my 3greats-grandmother. 

On her marriage to John Pearce she states that her father is James Turner and he is a Plasterer. 

John is also Irish - but I don't have any idea where in Ireland he might be from. His father is Richard Pearce and they are both bootmakers. John dies in 1844 so unfortunately is only on the 1841 English census. 

I've looked on Ancestry for Mary's baptism but so far haven't found a Mary with a father James in Cork. 

Although I've been researching my tree for more than 20 years I've only recently found more on these Irish lines so I am very grateful for any help or suggestions in finding more on my ancestors in Ireland.