Civil registration in England began in 1 July 1837, so only records from that date can be found. In practice, there was a slow start and it was not compulsory until 1875.
The whole of the West Penwith district comes under the remit of the Superintendent Registrar for Penzance. The address is
The records held at this office have the distinct advantage that they are often the originals. They are held chronologically and, in the case of the marriages, are by parish (or register office) as they were originally written. These marriage records should be duplicates of the parish marriage register where they exist.
There is a good and official guide to using these local Registry offices on the County Council Family History page.
The records of the General Register Office are held in Southport but are not directly accessible. These are contemporary copy records made locally and deposited regularly. There used to be indexes available to view at Somerset House, then St Catherine's House and lastly at Myddelton House but these have now all closed. Microfiche copies are held at the National Archives in Kew and at many local record offices, public libraries and also, to order, from LDS family History Centres. Full details of official sources can be obtained from the GRO web site. which also gives addresses and information on how to order certificates. There are also a number of online sources of the indexes listed there, some of which are free and some of which charge.
The indexes are arranged by quarter year for the whole of England and Wales in large hand-written, typed or printed books. When using them, care must be taken to allow for late registration and transport delays spilling the required record into the next quarter. After 1984 the indexes are aranged by year.
The reference numbers obtained from any of these indexes are not usable at the local registry office who have their own system.
This is a summary of what you can expect to find on the indexes of each type. A description by Barbara Dixon of the detailed contents of certificates and what they mean can be found at England and Wales Birth, Marriage and Death Certificate Information. This is now also available as a book
A resource worth watching is the FreeBMD project which is (slowly) putting the indexes online and also has a partial list of the locations of copies of the indexes. For Cornwall, all volume numbers are IX until 1851, 5c after that date.
The first volumes contain only surname and as many forenames as fit in the space together with the registration district, the volume and page number. From September 1911 the mother’s maiden name is also included, but reduced space is available for forenames, so they are often reduced to just one, perhaps with initials.
The GRO also has indexes of adoption from 1927 and some miscellaneous records.
The bride and groom are indexed separately and will have the same reference numbers (a good cross check). The first volumes contain only surname and as many forenames as fit in the space together with the registration district, the volume and page number. From March 1912 the spouse’s surname is also included, but reduced space is available for forenames, so they are often reduced to just one, perhaps with initials.
The GRO also has indexes of civil partnership from December 2005.
The first volumes contain only surname and as many forenames as fit in the space together with the registration district, the volume and page number. From 1866 the age at death is also included. From 1969, if you need information this late, the date of birth is also included.