The Richard Costain who was one of the 2 founders of the construction company, lived in his later years at Blundellsands, Liverpool, and his 1902 death was registered in West Derby:

England & Wales, FreeBMD Index: 1837-1983 Record
about Richard Costain

Name: Costain, Richard

Record Type: Deaths

Age at death: 63

Quarter: September

Year: 1902

District: West Derby

County: Lancashire

Volume: 8b

Page: 197

It's possible that his body was brought over to the IOM for burial, though I'd have guessed Arbory as the most likely burial place. St Lukes, Baldwin doesn't seem likely.

However, I'd guess that it's much more likely that he'd have been buried at or near Blundellsands.

Jean C