How do you know the correct form for changing a place name to an indicator of it’s denziens? Eg London -> Londoner, Bolton -> Boltonian

I did manage to find some helpful-looking articles on Wikipedia:

• An article on demonyms (“name for a resident of a locality which is derived from the name of the particular locality”)
• A list of adjectivals and demonyms for cities. Sadly Bolton isn’t included in the list or any others I could find.

However, the first article on demonyms has, if not rules, then patterns of demonym formation for English names. The examples of Washington and Wellington (although not British place names) would suggest Boltonian (although the example of London>Londoner does not). A Google search would seem to suggest this is being widely used, and this is confirmed beyond doubt by an Urban Dictionary entry for Boltonian.

What, though, is the demonym for Sandy? What are people from Sandy, Bedfordshire called? @ostephens suggested Sandian, Sandite, and Sandpeople. I have been thinking about this and compiled a list of candidates, some of them based on the suffixes in the Wikipedia article:

• Sand
  
• Sandian
• Sandyan
• Sandeian
• Sandyean
  
• Sandine
• Sandyine
  
• Sandite
• Sandyite
• Sander
• Sandyer
• Sandish
• Sandyish
• Sandene
• Sandyene
• Sandard
• Sandyard
• Sandese
• Sandyese
• Sandi
• Sandic
• Sandyic
• Sandivian
• Sandinavian
• Sandwegian
  
• Sand People
• Tusken Raider
• Harenosian
  

Notes: Sand is formed after the pattern of Germany>German, Turkey>Turk. Sandeian is based on the form of the name used in the Domesday Book: Sandeia. Sandyean is based on the old name of Sandy before the railways changed the spelling: Sandye. Sandwegian would probably better suit someone from Sandwich. I am not sure what the singular of Sand People would be: Sand Person? For Tusken Raiders, see Wikipedia again. Harenosian is from the Latin for a Sandy place: I have probably completely misunderstood the translation of this word.

Interestingly, a Google search for the word Sandyite shows it to be used quite a bit for Sandy, Oregon. A similar search on Bedfordshire doesn’t do anything. Neither do any of the other plausible ones (that I could be bothered to look up). However, I do have three favourites:

• Sandyite. Sensible favourite. It seems weirdly natural and is also being used in another Sandy. However, sounds a little like ready-made mortar.
  
• Sandeian. Elegant/historical favourite. It suggests a nicer pronunciation: San-day-un rather than San-dee-un. It is also pleasantly hard to spell. Plausible alternatives I like are Sandyean (also pleasantly hard to spell and with some historical overtones), and Sandian.
• Sandinavian. Say no more.

Any suggestions, comments, or actual knowledge?