Donna - been doing a bit of work on your problem so let's take a look at a few things to ensure I have the right people.
1861 Census, Chyandour, Penzance
William Hocking, head, mar, 74, labourer, St Paul
Ann do., wife, mar, 73, St Just
Susan do., daur, unm, 29, Penzance
Sarah J. do., grandaur, 6, scholar, Madron
1851 Census, Chyandour
William Hocking, head, mar, 64, farm labourer, Paul
Ann do., wife, mar, 63, St Just
Edward do., son, unm, 21, farmer, Penzance
Samuel do., son, unm, 21, farmer, Penzance
Susan do., daur, unm, 19, Penzance
1841 Census, Coomb(?), Madron
Wm Hocking, 56, ag lab
Ann do., 50
Fras do., 20, blacksmith
Mary do., 15
Jos do., 15
Saml do., 12
Edwd do., 12
Susan do., 10
(I am wondering if 'Jos' was meant to be Thomas?)
Also found the following baptisms at Madron:-
Margery Hocken bp. 23rd October 1808
John Hocken bp. 4th February 1810
Francis Hocking bp. 22nd March 1818 (of Tregavarah)
Mary Ann Hockin bp. 31st March 1822 (of Tregavarah)
Thomas Henry Hocken bp. 18th September 1825 (of Tregavarah)
Edward Hocking bp. 8th November 1829 (of Penzance)
Samuel Hocking bp. 8th November 1829 (of Penzance)
Susan Hocking bp. 10th October 1831 (of Penzance)
If this is the correct family, as it appears to be, then I need to search for the baptisms of five further children.
I cannot find a burial record for Anne at Madron and my Penzance records only go up until 1844.
Now for a search for Anne's baptism.
Roy was quite correct in his message as the IGI records show that the Ann Warren baptised 18th February 1787 was indeed at St Just in Roseland which indicates you have possibly been given some incorrect information.
(She was the illegitimate daughter of Elizabeth Warren.)
The only candidates we have (from IGI) that are anywhere close would be:-
Ann Warren bp. 8th March 1785 St Just in Penwith d/o John and Patience
Anne Warren bp. 14th September 1788 St Buryan d/o William and Johanna
Ann Warren bp. 16th September 1790 St Just in Penwith d/o Richard and Susanna
Ann Warren bp. 29th May 1791 St Just in Penwith d/o William and Eliz.
The only William Hocking baptised at Paul between 1781 and 1791:-
William HOCKIN bp. 16th March 1788 Paul s/o John and Anne
Others in the right time-frame and general area:-
William HOCKIN bp. 11th April 1784 St Just in Penwith s/o Simon and Jane
Warren marriages that are possibilities:-
William Warren m. Susanna Olivey (of Madron) 8th April 1776 St Just in Penwith
Edward Warren m. Anne Peake 17th August 1782 St Just in Penwith
William Warren m. Elizabeth John 31st May 1784 St Just in Penwith
Other than that I am having no luck without searching through every Marriage Register for which I have a transcript.
It is still 'possible' that the 1787 baptism at St Just in Roseland is the correct one.
But, if so, we would then need to identify Elizabeth Warren.
She may have been in that area with relatives for the birth of her child and it does still explain Anne naming her birthplace as St Just in the Census.
Best I can just for now.
Ian