Using FreeBMD.org.uk, I can't see any marriage, anywhere in England & Wales?
Likewise, the only Minnie births I can see are:
December qtr 1878
Guildford Registration District vol 2a, page 77
Holt, Minnie
June qtr 1879
Manchester Registration District vol 8d, page 302
Holt, Minnie
The Index Search at GRO.gov.uk, now includes Mother's maiden name on nearly all births from 1837 until 1915.
There are no Holt births, with a mother's maiden name of Hardy, 1876-1880?
The 2 births mentioned above have a MMN of Tayman and Flevelle respectively.
There are the following Birth Registrations for William Henry Holt, in 1854
March qtr, Manchester Registration District
June qtr, Haslingden RD
June qtr, Saddleworth RD
September qtr, Walsall RD
September qtr, Haslingden RD
December qtr, Chorlton RD
Plus another in 1853 and another 5 in 1855

(All to be found using FreeBMD)