Hi Omega and Jan,
Thank you Omega, for looking that up;
The "Allen" could actually have been their daughter Ellen/Eleanor, named after her mum. Again, with the name Allen, I found no trace of the existence in any BMD records afterwards. "Elen" was found with her father in the 1841 and is absolutely definitely with her married sister Sarah in 1851 (marked as "sister") so I have no doubt Ellen was John's daughter.
However, did it definitely say Allen was a son? (This is a bit of a mystery because we generally absolutely beleive the parish records!)
I had in mind I should add the date of the wedding and then forgot to put it in - it was 2 March 1813 at St Nicholas Church, and Andrea kindly checked that and gave me the witness names.
If either of you are willing, I'd be really happy if the baptisms could be checked between 1813 and Dec 1826 because of this type of anomaly and to see if there were two Johns and any other children.
Thanks again,
Penny
(1851:
1851 Thornton Hth, Croydon, Surrey
Anthony Cowdry born by my calcs abt 1824 Burrstow, Surrey, Head
Sarah Cowdry born by my calcs abt 1821 Worth, Sussex, Wife [nee Dancy]
Anthony S Cowdry born by my calcs abt 1845 Worth, Sussex, Son
Alfred W Cowdry born by my calcs abt 1847 Croydon, Surrey, Son
Ellen M Cowdry born by my calcs abt 1849 Croydon, Surrey, Daughter [named after grandmother]
Elenor Daney born by my calcs abt 1822 Worth, Sussex, Sister )