By law, a fee can not be charged for viewing marriage registers still held by the incumbent. However, you may find it difficult to get the incumbent to obey the law.
The above are the fees if the incumbent performs the search, not if a member of the public performs the search himself.
What makes you assume that a fee can not be charged for viewing marriage registers still held by the incumbent?
Perhaps you can quote the specific Act that makes that law as I would be very interested to see it.
I wonder if you are confusing searches in the marriage register with the laws on Simony, which forbid the charging of fees for a sacrament?
It has certainly since 1836 been enshrined in law that the public have to pay to make searches in marriage registers.
The 1836 Act puts it this way-
XXXV. And be it enacted, That every Rector, Vicar, or Curate, and every Registrar, Registering Officer, and Secretary, who shall have the keeping for the Time being of any Register Book of Births, Deaths, or Marriages, shall at all reasonable Times allow Searches to be made of any Register Book in his keeping, and shall give a Copy certified under his Hand of any Entry or Entries in the same, on Payment of the Fee herein-after mentioned ; (that is to say,) for every Search extending over a Period not more than One Year the Sum of One Shilling, and Sixpence additional for every additional Year, and the Sum of Two Shillings and Sixpence for every single Certificate."
Note it states 'allow Searches to be made' rather 'will make searches', that shows that the public are entitled to search the registers on payment of a fee.
The fee was part of the living, income the incumbent used to live on as the Church did not pay wages.
Cheers
Guy