Two usefu sources of areas where 142 operated are in two books on Pacers -the Pacer by Mackin -largely captioned photos and The Pacer Family by Kerr which has more detail and many photos from around the country and various liveries. There is also a Modern Locomotives Illustrated on the subject.
Examples of 142s in Cornwall, North East, Darlington-Saltburn, Carlisle-Lancaster, Blackpool, Leeds, York, Sheffield, Liverpool, Wales.