You can take a bus from Monmouth to Lydney via Coleford, Angel Hotel in around 1 h 22 min.
How to get from Monmouth to Lydney
From Monmouth, Bus Station (Monmouth Bus Station) bus to Coleford, Angel Hotel then line 23 bus to Lydney, The Orchards. 1 h 22 min £4. From Monmouth, Bus Station (Monmouth Bus Station) bus to Chepstow, Bus Station (Chepstow Bus Station) then line 755 bus to Lydney, Tesco. 2 h 7 min £9. From Monmouth taxi to Lydney. 23 min £56. From Monmouth drive to Lydney. 23 min £2.