When I couldn't find Godfrey's birth in IOM records (you didn't give his age), I had a look at the 1871 census:
Name: John Wallace
Age in 1871: 37
Estimated birth year: abt 1834
Spouse's name: Catherine Wallace
Where born: Edinburgh, Scotland
Civil Parish: Jurby
County/Island: Isle of Man
Country: Isle of Man
Registration district: Isle Of Man
Household schedule number: 3
East Nappin Cottage, Jurby:
Household Members: Name Age
John Wallace 37 schoolmaster b.Edinburgh
Catherine Wallace 43 b.Jurby
Margaret E Morrison 10 step daur b.Jurby
Christian Morrison 8 step daur b.Jurby
William Wallace 2 son b.Jurby
John Wallace 6 Months son b.Jurby
Ellen J Cleator 10 niece nurse b.Jurby
[Parents married in Jurby 1868.]
In 1881 [FamilySearch]:
John WALLACE Head M Male 47 Scotland School Master
Catherine WALLACE Wife M Female 51 Jurby, Isle of Man, England Sempstress
William WALLACE Son U Male 12 Jurby, Isle of Man, England Scholar
John WALLACE Son U Male 10 Jurby, Isle of Man, England Scholar
Margaret E. HARRISON Stepdaur U Female 20 Jurby, Isle of Man, England Dress Maker
Christina HARRISON Stepdaur U Female 17 Jurby, Isle of Man, England Pupil Teacher
Joseph CLARK Boarder U Male 3 Douglas, Isle of Man, England
Source Information:
Dwelling Baldrine Rd
Census Place Lonan, Isle of Man, Isle of Man
Family History Library Film 1342346
Public Records Office Reference RG11
Piece / Folio 5602 / 4
Page Number 2
[Interesting - Morrison to Harrison. Def. Morrison in 1871]
In 1891:
Name: John Wallace
Age: 57
Estimated birth year: abt 1834
Relation: Head
Gender: Male
Where born: Edinburg, Scotland
Civil Parish: Lonan
Ecclesiastical parish: Lonan
Town: Apneash [Agneash]
County/Island: Isle of Man
Registration district: Isle of Man
Sub-registration district: E
ED, institution, or vessel: 4
Ballabeg, Lonan:
Household Members: Name Age
John Wallace 57 Widr schoolmaster b. Edinburgh
John Wallace 20 son assistant teacher in school b.Jurby
Margaret E Morrison 28 step daur dressmaker b.Jurby
Christina Morrison 27 step daur schoolmistress b.Jurby
Joseph C Clarke 13 boarder scholar b.Douglas
Sidney Morrison 2 grandson b.Lonan.
Sydney MORRISON 8 Mar 1889 Lon [Father] Not given [mother] Margaret Elizabeth MORRISON [BL's index].
IGI has South Laxey Hill, Lonan, Isle Of Man, and spelt "Sidney".
So where was Godfrey? Was he Sidney, mistranscribed from (or on) the gravestone?
No doubt someone will check it and the memorial for you and the mystery will be solved!
Sue