Hi Joanne
I've found them in the hamlet of Aldreth, Haddenham parish under ref RG9/1037 folio 112, but confirmimg what Frances found it doesn't look as though Read Peacock was the father. The census page is a bit confusing as the enumerator has not described anyone on the page as "Head", merely Father, mother, bachelor, widow etc in the Relationship to head column. I'll give you all the Peacocks on the page as they are doubtless connected:
Farm House, Aldreth Schedule no. 2
Read Peacock father married 74 born Aldreth
Martha Peacock mother marr 76 farmer of 11 acres land born Aldreth
Private House, Aldreth, Schedule no. 5
John Lattemore bachelor 66 ag lab born Aldreth
William Peacock father married 19 ag lab born Aldreth
Martha Peacock mother marr 19 wife of ag lab b Haddenham
Alice Elizabeth Peacock child 1 month b Aldreth
Private House, Aldreth, schedule no. 6
William Peacock widower 63 ag lab b Girton, Cambs
Mary Peacock widow 30 pauper b Willingham Cambs
Joseph Peacock grandson 8 scholar b Aldreth
Mary Ann Peacock granddaughter 6 scholar b Aldreth
Harriet Peacock granddaughter 5 scholar b Aldreth
Other Peacocks in Aldreth/Haddenham
Folio 114
Private house, Aldreth
Sarrah (sic) Peacock head widow 43 b Aldreth
James Tale/Tall/Sale? son unmarr 20 farmers lab b Aldreth
Thomas Peacock son 13 farmers lab b Aldreth
Richard Peacock son 9 farmers lab b Aldreth
Folio 119B
Private House Aldreth
John Peacock head marr 37 farmers lab b Aldreth
Caterine Peacock wife 36 b Aldreth
Mary Ann Peacock dau 10 scholar b Aldreth
I've had a look at the NBI but unfortunately entries for Haddenham stop at 1837.
Regards
David