Doh, forgot the +, should of been an easy one to spot

DECLARE @Latitude float = 8.4827

DECLARE @Longitude float = 76.9192

DECLARE @ID int = 1

UPDATE [MarvelTour_DEV].[dbo].[LocationCopy]

SET

LocationGeography = geography::STGeomFromText('POINT('+@Longitude+' '+@Latitude+')', 4326)

WHERE LocationID = @ID