Had a similar issue with my starter last year. Main dealer wanted silly money for the new motor (fitting was cheap by comparison) but was happy to fit an exchange one i got from euro car parts. It was quite funny really. The mechanic told me what to get and gave me all the codes and euro car parts were just across the road!. Had to be secretive though so his boss didn't find out.....bit like a WWII movie, hiding it under my coat...LOL
Anyhow, miles cheaper and works a treat. Personally I wouldn't go for second hand unless you know its come from a working vehicle and you can see it running. Also, be careful as I think there were a couple of different versions with mounting holes in different places so make sure you get the right one. If you get it from somewhere like ECP just speak to them and agree that you can change it if it's not the right type (unless you can take the old one in with you)
Good Luck
Rob
22 C4 1.6 eHDI Shine Plus
67 RR Autobiography 4.4 SDV8
15 C4 1.6 eHDI 115 Exclusive - fond memories
12 RR Westminster 4.4 TDV8 - Gentleman's Club on wheels
05 C5 2.0 HDI 138 Exclusive - gone but not forgotten
05 C5 2.0 HDI 138 VTR - crushed May 2015
Trev, try this firm. I've used them a couple of times and have nothing but praise for them. The recon'd motors look like new and their prices are fantastic.