Box Lane Chapel - note the stone alter tombs and the wooden burial board - which do not survive many years.
A large number of memorials have been recorded
by the Hertfordshire Family
History Society, and details are given on their web site. Their
excellent booklets are very cheap.
If that fails Gerrish indexed many graveyards in about 1900. (The Hertfordshire Family History Society booklets mention tombstones listed by Gerrish but no longer present). I know that the original notes are available at HALS and the Society of Genealogists Library has a microfilm index which may also be available at your nearest LDS Family History Centre.
Several of the books on the history of Hertfordshire include some church memorials and John Edwin Cussans' History of Hertfordshire, which was published in parts between 1870 and 1881 and was reprinted in three volumes in 1972, also includes inscriptions of the more prominent churchyard memorials. However I very much doubt that he included any from non-conformist graveyards.
However in many towns, and particularly as you get closer to major cities, the parish church graveyards rapidly filled up in the 19th century. Corporation cemeteries were opened, and some are still in use. These vast modern cemeteries are less likely to be indexed that then older and smaller church and chapel graveyards If you are looking for a specific named individual who may be buried in one of these "modern" cemeteries, and know the approximate date of burial (for instance from the death certificate, or will probate), a letter to "The Town Cemetery, c/o local town council" giving details may well result is a plan of the relevant part of the cemetery showing the location of the plot. However it is very unlikely that they would carry out a general search for a particular surname.
It is perhaps worth making the general point that before an index can go online, or someone can look something up in a book or on a microfiche, someone has to collect and collate this data. It is therefore a good investment to join the genealogy society (and perhaps also the local history society) of the area you are interested in and help them in local projects. You should also purchase any of their relevant publications. Without the work done by such societies in the past, and without investment for the future, the indexes which those who live overseas find so useful would not exist!
See Burials, Town Cemeteries and Looking for 20th Century Burials
See also The Condition of Hertfordshire Graveyards
For War Memorials see War memorials and Rolls of Honour
Page updated September 2011