Hi,
In 1834 there is a Purcell family listed in the Tithe Applotments for Ireland. This is the only Purcell in Kilcommon. his name is William. He may have been a brother to John or even his Father.
The only place you may get your info is in Ballina, the county town of Mayo.
I did see a tree in Ancestry that has the children's names as POSTLE, even though the Church record states Purcell.
In the Griffiths Valuation there is a William, George and Robert listed.
Tithe and Griffiths are lists compiled for Taxes, rents and land from 1823 to 1839 and 1839 to 1864. They are in a town land called Glinsk, Belmullet.
If you search for a heritage place for this area, email them and they should be able to help.
There is a death for a Ann Purcell on the 30th May 1866 in Lyng, Mitford, Norfolk, England. She was 86, so born about 1780. A Will was also listed and it says that a Henry Buck was the sole Executor. Going by 1780 and Ann born in Lyng, I saw 1851 and 1861 census records, then Ann born in Lyng, there was another name Sarah Ann born 1782, she may be Ann's sister. Her name was Kendall. I am not saying it is.
So you will have to look at the Churches in Lyng and I am sure you will get your info. from there.
I hope this is a help for you.
Maggsie