Hi Paul,
I couldn't find any soldiers at all by the name of Snook on the Waterloo roll I'm afraid. And looking at your original post again (his wife was a widow by 1841), he's not going to appear on the MGS roll as the medals were only issued to survivors in 1847.
I did check the MGS roll anyway for other soldiers called Snook, just incase they might be related (possible lead?). There's one listed, as follows:
Private Thomas Snook, 4th Dragoons (bars for Talavera, Albuhera, Salamanca, Vittoria & Toulouse).
Sorry can't be more help.
Neil