Hi UKgirl,
further to your request to re-post a previous link i posted elsewhere, here goes
Found this on a site
http //www gmcro co uk/catalogues/userguide/public htm link brokenWhen you get to the site use Edit - Find - Prestwich on your toolbar
A/PRES/ PRESTWICH HOSPITAL
Patient Records Patient Casebooks 1891 - 1913; Private Patients Casebooks - Males 1851 - 1905, Females 1890-1924, Index 1885-1919; Chronic Patients Casebooks - Males 1857-1914, Females 1855-1904;
Notice of Death Books 1891-1960; Registers of Deaths 1894-1948; Death Books Addresses of Relatives and Friends 1940-1964; Admissions Registers 1851 - 1951; Civil Registers - Certified Male Patients 1907-1935, Certified Female Patients 1907-1948, Voluntary Patients 1935-1948, Temporary Patients 1941-1948; Registers of Removals, Discharges and Deaths 1893-1906; Discharge Registers 1893-1946; Registers of Departures, Discharges and Transfers 1907-1945; Registers of Departures, Discharges and Deaths 1949-1973; Register of Patients Discharged to Friends 1909-1926; Escape Books 1851-1860, 1891-1970; Index Books 1893-1974; Index Books, Transfers to Rochdale Workhouse (Females) 1893-1917;
Possible the death could be in the bit i've highlighted in red
Some background on the History of Prestwich Asylum
http://www.manchestereveningnews.co.uk/news/local-news/exhibition-tells-the-history-of-towns-asylum-891671best wishes
Tony