There were 50 class 50 locomotives built. 18 have made it into preservation, of which 12 are operational, 5 of which are mainline certified. Perhaps that's the highest proportion of any diesel class preserved??
Oops - it was 11 years
and 1 month ago that the suggestion that GoCo (as it was named at the time) were looking to start a loco hauled service from Yeovil Junction to Oxford using class 50 locomotives and coaches - reported at
http://www.passenger.chat/8313 . I rated it as "extremely unlikely" that you would see this regularly - though it could have been a good option for a demonstration / proof of principle run.
So - with my error - not something from
22nd February 2011. oops.