OC, you need to look at the London Gazette
http://www.gazettes-online.co.uk/
Choose London and Advanced search. Put William Whittaker in the exact match box and Garlick in the next box. You should get four matches and three are your man. This computer (OH's) is being difficult, but I did manage to see one of the pages which says Wm was in Lancaster jail!! I can't view that page at the same time as typing here so it's frustrating. Two of the entries are in 1843. so I'm thiking he was alive then.