Having a few free credits for the genealogy record site ScotlandsPeople I looked up the Eisners and found dates of death for them, if they are of interest.
Deaths
Last name, forename, age, year of death, place
EISNER, Emily Elizabeth, 77, 1968, Perth < --- Frank's wife b. 1890 (ref 1939 Register) maiden name Mickova or Miekova *
EISNER, Frank Joseph, 81, 1971, Perth < --- Frank Eisner b. 1889 (ref 1939 Register)
EISNER, Kathleen Nichol, 67, 1996, Perth < --- Eric's wife b. 1929 married 1952 Northumberland South
EISNER, Eric Carl, 79, 2006, Perth < --- Frank's son Eric Eisner b. 1926 Wakefield (one of twin boys, the other died age 5)
There are descendants of Eric still around. I have names if anyone wants to try and contact them for more info.
* No idea where Emily and Frank were married. No marriage shows up for them in British or Irish records. Maiden name is shown in birth record for Eric and his twin.
There is a record in the National Archives about Frank's naturalisation in 1919:
Nationality and Naturalisation: Eisner, Frank, from Czechoslovakia.
Resident in Birmingham.
Certificate 4,740 issued 23 September 1919.
In 1939 Frank and Emily are shown as living in Newburn R.D., Northumberland, presumably whilst Frank was working at Lemington Glass as per his BEM citation in the London Gazette:
SUPPLEMENT TO THE LONDON GAZETTE, 9 JANUARY, 1946 page 323
Awarded BEM 1st Jan 1946 - Frank EISNER, Glassblower, Lemington Glass Company