Here is part of an early example from the IOM of someone changing his name, which we wouldn't have known about if his wife hadn't petitioned the court at the time of his decree.
[Full transcript at: www.iomfhs.im/lawsons/LawsonBMD/twill/1731_003.html]

"..... To the Revrd Mr John Woods and Mr
John Cosnahan Vicars Genl
The humble petition of Catherine Creer of
Ranscalt in KK Braddan

Herewith That your petitioner is apprehensive~
She is like to have some trouble in relation to her
Marriage with John Creer lately deceas'd. Therefore she most humbly begs
that her evidence relating to that affair may
be taken… which granted she as in duty
bound shall pray, etc. ----

At Consistory Court held in
Douglass, March 26. 1735

Thos. Banks of Kk Onchan maketh
Oath that he was in Liverpool abt thirteen
Or fourteen years ago. When John Creer a
Native of this Island, wth whom he was ac=
=quainted many years before, was marr'd to
Kath: Creer als Turner now prest. in Court,
wch John went by the name of Jon Wilson
in England ~ That the marriage was so=
:lemnis'd in the old church of the sd Town
& yt James Corlet of Ramsey gave the
woman as father or friend ~
The sd Thos. Banks further deposeth
that he knew the sd John Creer &
sd Katherine live together as man and
wife in Liverpool for some years
afterwards. and since then also in this
this Island, where sd Creer dyed.

Thos Banks his B mk
Taken by & before
Us John Woods
John Cosnahan

At KK Braddan March 28 1735

James Corlet of Ramsey Mariner maketh oath
that he was by & in place & stood as father of
the Marriage of John Creer als Wilson and
Katherine Turner ~~ That the sd couple were
marry'd in the old Church of Liverpool about 14
years ago by the Revd Mr Bell then Rector or
Minister of the sd Church ~~ And this Depont
further adds that he knew the sd couple vizt
John Creer & Kath Turner live together
in Liverpool for several years afterwards
and since then also in this Island. And
that this Same Creer was the very man
who amongst the Mancks men here &
in Liverpool went under the name
of Creer Wilson

Jams. Corlet his mk X
Taken by & before me

John Cosnahan"

So apparently he called himself both John Wilson and Creer Wilson in England, including being married as Wilson, and was also known as Creer Wilson as well as John Creer after he returned to the IOM.

Familysearch has their marriage on 30 January 1722 Saint Nicholas,Liverpool,Lancashire,England.

Sue