I think your William was 50+ on the 1841 census (HO107/911/7):
Boycott, Pontesbury
William Blakemore, 50-4, farmer, Y
Frances B, 50-4, N
Matilda B, 15, Y
Frederick B, 15, Y
Ferdinand B, 14, Y
Lewesea B, 10, Y
Alfred B, 10, Y
There is a 68 year-old widowed William Blakemore, retired miller, living in Pontesbury in 1861. He was born in Asterly, Salop.
The 1851 entry has a 19 year-old Alfred with William, so they are probably all the same man, as Phanny is a variant of Frances.
Richard