Hi
The date for local newspapers flourishing was 1855 when the tax on paper was abolished.
https://wiki.familysearch.org/en/England_NewspapersThe earliest Croydon local newspaper appears to be the The Croydon Chronicle and East Surrey Advertiser which started in 1855.
If you put Croydon into the British Library newspaper search engine you get a list of all the newspapers they hold and the dates of publishing.
http://catalogue.bl.uk/F/?func=file&file_name=find-b&local_base=NPLOther than the shortly lived Crystal Palace Gazette; and Sydenham, Norwood, & Croydon Advertiser which published 2 editions in 1853 and the Surrey Mercury; Guildford, Kingston, Epsom, Dorking, Croydon, Reigate, Farnham & Chertsey Agricultural Journal (which would have concentrated on farming matters) 1845-1847 the only other newspapers would have been at county level and not even one county level.
The County chronicle, and weekly advertiser, for Essex, Herts, Kent, Surrey, Middlesex 1780-1841
Brighton Herald; or, Sussex, Surrey, Hampshire & Kent Advertiser 1806-1902
Regards
Valda