Preston had male suffrage long before the rest of England, since the 17thC possibly. Men over 21 who had been resident in the borough for a certain length of time could vote.

Exceptions were paupers and any man who had been convicted of crime. Preston got a special mention in the Great Reform Act 1832. Radical M.P. Henry Hunt represented Preston.
The poll book for 1830s & '40s is in Harris Library, Preston. 4 of my ancestors should be in it but I couldn't find them on a quick look.