I have now obtained my grandfather (TJ)'s Army Records and they're a very interesting read... To put it mildly, he was neither a good soldier nor one who believed in staying with the colours throughout his 18 years of active service (of which he spent 5 years either in a state of desertion or AWOL). He also lied through his teeth when he signed up about his marital status and the name of his next of kin (conveniently air-brushing his wife, child and parents out of his background).
They're a very convoluted set of documents but luckily there's a neat summary of his service in a letter to the Police in Winchester in late February 1954 (and why did they need to know, I wonder?)
He was released from Active Service to the Unpaid Army Reserve on 15 April 1946 and released from the possibility of further recall on 10 Feb 1954 (when he would have been approaching 49).
I'm still trying to track down his death, so my key question is: when the Army marked somebody's records as "Attains age of 4[5?] No further liability for recall" did they know he was still alive at that time, or was it a purely clerical exercise? Did soldiers in the Reserve have to keep the Army informed if their contact details changed (fat change TJ would have done this, I suspect, although the records for my father, who completed his National Service in 1948 and was also discharged from the Reserves in 1954 recorded a number of changes of address in between 1948 and 1954, so there was apparently some mechanism for notifying changes ...). Did they need to attend any regular activities? Or could a reservist die without his record being updated.