Hi Sue
Good to be of help.
The 3 St Helier Chapman births are:
Heather Jean Patricia Chapman, 22nd June 1923 at Premier Tour. Father - Charles James Chapman and mother - Jeanne Marie Lerat(??). The writings terrible! Reference volume 59 page 81.
Laurie Samuel Carter Chapman, 9th November 1922 at Pier Road. Father - no name, mother - Ethel Annie(?) Chapman. Reference volume 59 page 51.
Audrey Irene Nancy Chapman, 3rd July 1921 at 20 Broad St. Father - Wilfred James Chapman and mother - Mary Annie Beatrice Carter. Reference volume 58 page 91.
Electoral Roles still remain with the relevant Parish's. However most of them don't exists any longer and I wouldn't recommend going down this route as it will prove fruitless.
Stewart