Think I've solved the mystery of the Gildersleeves at Saxmundham.
It would seem that the majority of the parish records have the name as Gilders!
A John Gildersleeves married a Mary Turner 23rd May 1774 Saxmundham and they had the following children all baptised as Gilders:
John bp.17/3/1775 - bur.10th July 1794 as Gilders
Joseph bp.5th January 1779 - married Susan Mayhew 16th November 1814 Saxmundham as Gildersleeves, 1841 census has them as Gildersleeves, but Joseph buried as Gilders 30th May 1849.
Twins - Audley bp.20th August 1780 bur.1st August 1780 (?)
Thomas bp.20th August 1780 bur.1st August 1780 (?) Clearly, something wrong with dates
Mary bp.24th August 1781, bur.9th December 1781
Thomas bp.24th November 1782
Robert bp.30th October 1785 - married as Gildersleeves to Sarah Uiett (?) 15th May 1811 Benhall, Suffolk - bur.7th July 1811 Saxmundham as Gilders!
Having now realised that the Gilders/Gildersleeves were one and the same family I then rechecked and found your Williams baptism:
William Gilders bp.23rd June 1811 Saxmundham, son of Robert Gilders and Sarah Whyard.
Two weeks later Robert dies and it looks like his widow remarried as Sarah Gildersleeves to a James Ward 7th April 1820 Saxmundham and the Wards had the following children:
Robert bp.16th July 1820
Charles bp.3rd June 1822
Emma bp.9th November 1823
George bp.12th December 1825
Rebecca bp.13th February 1827
1841 Census shows James (journeyman shoemaker), Sarah (bc.1791), Emma and Rebecca living in Woodbridge, Suffolk. (Haven't checked to see what became of the other children.)
By 1851 James Ward is a widower - Sarah Ward bc.1786 bur.14th December 1844 Woodbridge.
John Gilders bc.1749 bur.31st January 1811 Saxmundham
Mary Gildersleeves bc.1741 bur.31st March 1820 Saxmundham.
Where John Gilders/Gildersleeves was born/baptised I don't know - doesn't appear to have been at Saxmundham.
Annette