Thanks to everyone who replied.
The name variations: LAAN is the usual spelling at the time in Lowestoft PR, and CUNNINGHAM/CULLINGHAM seems to have been used interchangeably. I have ample proof in both cases that the variations as used refer to the same person.
Trish - You are correct. For this to be my couple, the age at burial for both Mary and William would have to be incorrect.
Annette7 - details surrounding the Mary LAAN and William SALLOWS marriage are:
The SALLOWS/LAAN marriage was in Lowestoft 24th March 1776. The IGI transcription does NOT have any status for bride and groom, nor parents names. ("England Marriages, 1538–1973 ," index, <i>FamilySearch</i> (
https://familysearch.org/pal:/MM9.1.1/NXT5-N6T : accessed 08 Oct 2014), William Sallows and Mary Laan, 24 Mar 1776; citing St. Margaret, Lowestoft, Suffolk, England, reference 151; FHL microfilm 1526139).
There are 2 separate entries for the marriage in IGI with different, but close, dates so I think the IGI info comes from a banns book, which is NOT on "England, Norfolk, Parish ...Record Office), 1510-1997, Lowestoft St Margaret"
When James LAAN was Chr in Lowestoft 18th May 1768 he was the son of Samuel and Mary LAAN. When John LAAN was Chr in Lowestoft 13th April 1770, he was the posthumous son of Samuel and Mary LAAN. I checked all original pages between the conception of James and the birth of John, and there is no burial of Samuel. I am assuming his death, based on the 'posthumous' note in 1770, as I believe this proves that Samuel was dead by 1770.
The marriage falls outside the coverage of the original Norfolk <sic> PR on the Family Search site, but the mother's name is Cunningham on Mary SALLOWS' Chr in 1787. I believes this indicates that the Mary nee CULLINGHAM who married Samuel LAAN could well have been the Mary LAAN who married William SALLOWS. The names and the dates fit.
Annes - as you can see from above, the ages at death of the couple buried in Kessingland are in question. I will be grateful for anything you can tell me from the Suffolk record office, but as this is only me trying to cover off a negative to eliminate them, please give this a LOW priority.
Thanks again for this great Suffolk list - Shirley