As there was a few questions about the class 59s on the new Hornby 67 thread I thought I'd do a quick summary of the class as they are a firm favourite of mine. Essentially there are three different variations of the class 59; 59/0, 59/1 and 59/2.
59/0
These were the first 59s build by EMD in La Grange for Foster Yeoman. Four were built in 1984 with a fifth coming in 1988 as FY were unhappy with the poor reliability of BR locos such as the class 56 at the time. They were the first privately owned locos to run on BR metals. They featured centre mounted headlights under the cab windows and different marker lights from subsequent batches.
They were all delivered in Foster Yeoman livery, pictured here http://www.flickr.com/photos/donglos/4976383991/
One of the original class, 59 003 was exported to Germany, renumbered as 259 003, and operated by Yeoman/Deutsche Bahn (DB), pulling stone trains. Picture of it here - http://www.modern-locoillustrated.com/MLI%20issue%20downloads/Issue%20173/59003Eastleigh.jpg
It has since moved on to Heavy Haul Power International and is operating in this livery in Germany http://farm6.static.flickr.com/5097/5451528031_ce9dace62f.jpg
59/1
Foster Yeoman's main competitor ARC were impressed by the 59s and decided to buy some of their own. In 1990 four 59s were built, this time in EMD's London plant in Ontario, Canada. Designated 59/1, they featured revised lights each end, losing the centre beams the 59/0s had, and getting lights similar to the first 66s.
Picture of the original ARC livery here - http://mike-walker.smugmug.com/Trains/Mendip-GMs/i-pT227WT/0/M/R-BR-852ARC-59103-Old-Oak-M.jpg
59/2
Following Foster Yeoman, National Power decided to investigate the possibility of running its own trains, by ordering a single pilot locomotive. Following the trial, National Power ordered a further five locomotives and a fleet of hopper wagons to carry coal and limestone.
Again built at the London plant in 1994 and 1995, the six Class 59/2 locomotives differ from the Class 59/1s in several ways. A carbon dioxide fire control system replaces the original Halon system, NiCd batteries replace lead-acid, and the fleet all have drop-head knuckle couplers fitted. A more advanced slow speed control suitable for merry-go-round power station coal train operation has been fitted, as well as yaw dampers for a higher top speed.
These were the last of the 59s, orignal National Power livery - http://farm7.staticflickr.com/6031/6324851535_8d28f1a36f_z.jpg
In April 1998 EWS took over the National Power rail operations and re liveried the 59/2s into EWS http://www.semgonline.com/diesel/pics/cd59205_1.jpg and now they are all owned and painted in DB-S red http://upload.wikimedia.org/wikipedia/en/1/1a/59s-at-Acton.jpg
Mendip Rail
In the mid 90s both Yeoman and ARC pooled their resources and formed Mendip Rail. This became a train operating company to operate 59/0s and 59/1s on stone trains. The locos gained new liveries, such as Mendip Rail http://farm6.staticflickr.com/5449/7166192084_da18905c30_z.jpg Revised Yeoman http://farm4.staticflickr.com/3260/5761465652_43cfebd59c_z.jpg and revised ARC http://www.therailwaycentre.com/Main%20photo%20file/Cl59-1arc
ARC was then taken over by Hanson, and the 59/1s were repainted into their colours http://www.traintesting.com/images/59104%20Westbury%2019-10-06.jpg
Yeoman has also been taken over by Aggregate Industries, and the 59/0s are now being painted this livery http://www.therailwaycentre.com/NewSite%20POD%202008/POD30-07-08.jpg
All 59s work Stone trains in the South east, and can be regularly seen in London, mainly around Acton Mainline and the North London line.
Any questions/corrections/comments/additions accepted! Hope it's of help.