There is just one close match in 1851:
Water Lane, Crossens, North Meols:
Thomas Cropper. Head. 45. Ag Lab. N.Meols
Ann Cropper. Wife. 44. N. Meols
Richard Cropper. son. 23. Handloom weaver (silk). N.Meols
Robert Cropper. son. 20. Ag Lab. N.Meols
Alice Jane Cropper. Dau. 11. Scholar. N.Meols
Thomas Cropper. Son. 8. Scholar. N.Meols
Betty Cropper. Dau. 6. Scholar. N.Meols
The other nearest Thomas' in age in the census are aged 2 and 18, so I think we can establish that yours was son of Thomas & Ann.
Crossens was in North Meols, an old district which also covered South Haws, Marshside, Churchtown, Little London and others. The parish also covered Birkdale (though this was a separate village). In the late 1700's, the town of Southport developed close to South Haws from the increasing fashion for "taking the waters" and the demand for lodgings near the beach. Southport was, and still is, part of the old North Meols district. Once established as a fashionable centre, the old residential areas of Crossens, Little London etc became districts of Southport. Birkdale remained politically separate until the late 1800's, when it finally merged with Southport and became a further outlying district of the larger town.
So Thomas' description of birthplaces is accurate as North Meols, Crossens or Southport... as Crossens is part of Southport, which is part of North Meols... Liverpool doesn't count, however, so he lied there!
I have the full 1851 census for birkdale, North Meols, Ainsdale, Formby & Altcar, and there are a few Croppers in North Meols at the time, though it's not an old local name... this means that their church records won't be as easy to track down, as the common/long standing local names are available as one-name extracts from the family hitory society.
I have found what appears to be Thomas & Ann's marriage in IGI:
Thomas Cropper = Ann Blundell 12th Sept 1826. This ties in well with the age of the eldest child in 1851.
There's a close match in baptisms: Thomas Cropper, bap 25th Nov 1804. parents Richard & Alice (this matches the firstborn boy & girl names amongst Thomas' children, which helps to confirm the match).
Any help?
Impy