Searches on the National Archives site for Little Gringley and
Clarborough produced the following results:

Little Gringley:

GB/NNAF/O72550
Little Gringley Wesleyan Methodist Church
Little Gringley, Nottinghamshire
Scope: 1831-38: Sunday school records
Repository: Nottinghamshire Archives
Record Reference: MR1/305
NRA catalogue reference: NRA 17312 East Retford Meths
Clarborough:

GB/NNAF/O72568
Clarborough Primitive Methodist Church
Clarborough, Nottinghamshire
Scope: 1878-1966: minutes and accounts
Repository: Nottinghamshire Archives
Record Reference: MR1/520-34
NRA catalogue reference: NRA 17312 East Retford Meths
The Nottinghamshire County Council Archives page is not very informative as to access, other than providing contact details and opening times.

Sometime soon I need to set aside a few days mid-week and visit East Retford and Nottinghamshire archives in order to further research some of the leads I have found over the last 6 months.