If it helps, Gainsborough is/was in Corringham deanery. 
This would appear to be the CD-
Lincolnshire Parish Register Burials 1813-1900 Volume 3.
Ref: LIN-018C
Deaneries included are; Corringham, Graffoe, Lawres and Lincoln
The burial indexes CDs published by Lincolnshire FHS
usually cover only churchyard burials and not those in cemeteries.
Some of the larger cemeteries have indexes published on CD - Cleethorpes, Grantham and Lincoln ( the latter being split into two).
In addition the LFHS have published indexes for Boston, Bourne, Gainsborough North Warren, Grimsby, and Louth cemetery registers on fiche. I understand that the Boston registers will be published on CD once a further register which has been found at Lincs Archives has been indexed.