Hi,
Apart from the IGI and actually visiting the Berks Record Office, the only thing I can suggest is to request some research via Berks Records Office. They are very good, but it's not cheap. The Berks FHS have some name search facilities but - I think - not for baptisms. They may be able to help with marriages and burials. Check out the 2 websites -
http://www.berkshirerecordoffice.org.uk/familyhistory/index.htmhttp://www.berksfhs.org.ukAlthough it looks as if you have a similar predicament to mine - ancestors who spread themselves out over the Berks/Bucks/Oxon border! It's frustrating!

Anyway, I've had another look on the IGI -
James Harding = Sarah Gray 29/7/1793 Medmenham, Bucks (about 7 miles from Cookham)
Maria bp 23/3/1794 d/o James & Sarah in Medmenham
Then there's James in 1796 in Cookham & a submitted IGI for
John bp Cookham 6/2/1802
I can't find any more.
I would guess that Sarah died and James remarried to
Elizabeth Wix (Wicks?) 8/5/1802 in Cookham.
They then had (all Cookham):
John 6/2/1803
Ann 3/6/1804
William 20/4/1806
Thomas 3/9/1809
Going back further, there is a baptism for
James Hearding 28/4/1771 in Cookham, s/o James & Ann.
Hope this is of some help.
Jill