Not sure why you'd ride to Abbey Village from Great Hill. The best descent from there is to White Coppice, either ending at White Coppice itself, or veering right at the final tight left turn, then following a necky little path which meanders it way north. Or plenty of other options through the woods around Wheelton Plantation.
As for a route from Rivington to Healey Nabb, I've got two easy ones. From Rivington itself follow the bridleway to the east of Upper Rivington Reservoir that spits you out at the dam at the south end of Anglezarke reservoir. Then either ride across the dam on the road until the Yew Tree pub, turn right, then right again (signposted bridleway) at Kay's Farm, OR (cheekier option) ride to the right as you exit the bridleway and at the car park for Anglezarke, keep left, especially at the top of a short steep tarmac section, then follow good a good path, always keeping left around the edge of the reservoir until it drops you out near Healey Nabb.
(edited as Streetmap link failed)