Hi
Death certificates can be quite dodgy since their accuracy depends on the knowledge of the informant, who may not be a relative and may not know the exact age of the deceased.
Freebmd shows three Thomas Warman births in 1845: in Wells, Somerset, Jan-Mar, in Salford Apr-Jun, and in Chelsea Apr-Jun (Thomas Samuel Warman).
It may be that Thomas, born in Salford, did not die between 1891 and 1901 but just abandoned his family. I have looked on Freebmd for a Thomas Warman born 1845, who died after Mar 1891. Freebmd has two:
Jan-Mar 1917 Warman Thomas 72 Wells 5c 714
Oct-Dec 1929 Warman Thomas 84 W Ham 4a 182
I guess that the first of these is the one born in Wells - the second may be the one born in Chelsea but could be your Salford Thomas.
All the best
Gobbo