You are both very flattering,
I picked out two John Garrets, burials in Onchan (both aged 50 burials May 8 1838 and Mar 6 1841). This was because Marown, John & Margery married is close to Onchan. However as, like Sue, I found no suitable Johns or Margerys in the 1841 census, it is possible that they emigrated and that she returned alone to the island at a later date.
Also there is no Jurby parish christening for Margery Teare on the IGI, although there is an LDS submission for Margery Teare, daughter of John Teare and Ann Steven in Jurby on 24 March 1805.
I was unable to confirm how Catherine could have been the niece of Daniel & Jane Caley in the 1851 census. However, I found Daniel's marriage to Jane Kewley on April 16 1831 in Jurby, and when I looked up the christening info of Jane KEWLEY, I got another LDS submission: Jane COWLEY or Teare, christened July 25 1792, daughter of John Teare and Catherine Cowley. Possibly Jane and Margery were sisters or half sisters. although I am surprised that these christenings are not in the Jurby parish extracts. Kewley and Cowley could perhaps sound the same. There is no other IGI entry in Jurby 1792-1796 for a Jane Kewley. Note that Brian Lawson keeps the names apart on his site.