Roy, to summarise:
- Lydia was born in Upwell Norfolk - see above BMD entry
- In 1881 she and Thomas were at the same address in which you found them in 1891 - her PoB closely matches the 1871 family, and the Wisbeach District BMD entry
- In 1901, either she was missed in the headcount for the household of her daughter and son-in-law, or she is elswhere visiting ...
- The death record for 1911 is for someone of the right age.
I cant find her family in 1861 just yet, to be able to tell you who her mother was ...
Cheers, Newfy