Have you tried the IGI?:
http://www.familysearch.org/Eng/Search/igi/search_igi.asp?clear_form=trueThere's also a tool to allow you to search for a surname in a specific parish:
http://freepages.genealogy.rootsweb.ancestry.com/~hughwallis/IGIBatchNumbers/CountryEngland.htm#PageTitleHere's what I found on your family:
Mary Ann Bellamy, christened 27 May 1792 in Crowle. Parents John and Mary.
The couple could have been married just across the border in Yorkshire, as there's a marriage for a John Bellamy to Mary Coldthread, 13 June 1790 in Hatfield, Yorkshire.
Other christenings to the same couple in Crowle:
Mary Ann, 26 March 1791 (died in infancy?)
John, 28 May 1793
More christening occur later in Hatfield where they were married:
William Bellamy, born 30 December 1800, christened 29 March 1801
Isaac Bellamy, born 10 April 1804, christened 12 August 1804
The seven years gap suggests they lived elsewhere from 1793 to 1800.
There's a marriage for a Mary Bellamy to a Thomas Gileart, 18 May 1815 in Amcotts.
If you know where one of their children was born, just select the correct parish from the second link at the top and enter the surname. It'll give you all the christenings and you can see which ones are yours.