the most likely death for Allan looks like:
Jan 1988
Allan Henry Thomas d-o-b 15 Feb 1904
death registered Jan 1988
age 83
Gloucester ref 22 2135
now, I dont like to spend your money for you (!) but getting his will might be a good move, if he made one.
His wife has predeceased him, so it is likely he will leave stuff to his daughters. Now, depending on when he wrote the will (if he made one) it could well have the daughters married names. if you are really lucky it might have other snippets like addresses or grandchildrens names. Or , of course, he might leave everything to the Dogs Home, or not have made a will!
If there is one, there will also be, hopefully, th eaddress of the executor when the will was proved in 1988, so IF that is a daughter or son-in-law, you will get an address, albeit 20 years old.
Enjoy your day out!