You assumed correctly
1851 census 8 Graham Street Newington
John Lock 1826 Barnstaple, Devon,Head Clerk in Post Office
Maria Lock 1824 Bristol, Somerset, Wife
Jane Lock 1837 Newington, Surrey, Daughter
William Lock 1849 Newington, Surrey, Son
George Payne 1828 Bristol, Somerset, Brother-in-law Unmarried Clerk to Lawyer
Maria Payne 1793 Bristol, Somerset, Mother-in-law Widow
HO107/1567 Newington Walworth Folio 76 Page 37
Tricia