passenger compartment fusebox (electric rear windows)

[MO-MO]

im putting in electric windows for the rear, fitted the regulators, door looms, switches and made up my body looms.

-if my car already has driver and passenger electric windows,the only thing im having to worry about here is providing an earthing and a positive point for the rear two windows?

-now would i be right in saying, i could follow where the passenger and driver positive wires lead to, then il find the passenger compartment fuse box?

-would a bolt on one of the seats be a decent earthing point?

thanks
mo