u know one of them old american western trains, the ones u see in the cowboy films ( or the one used in back to the future 3)

your be lucky to find anything like that in South East London,
If you do it will be burned out and have had its wheels nicked!

Hmm, l do not think you will have a lot of luck - apart from anything else, locomotives like that are extremely rare and are in museums, but also you would not get away with all that smoke in London.!

If you really want a steam engine you could always look at:
http://prestonservices.co.uk/miniatures.htm
There is a Rio Grande K36 2-8-2 71/4'' scale steam loco there, and they are situated near Canterbury in Kent.

http://discoverlivesteam.com/

unless you want a model you got no chance. If you want a model try Kirklees Light railway they may be able to put you in touch with the old owner who had a model one that was steamed up, boiler certificate and running.
Or get a model railway magazine.

You've got to be joking! Unless it is a model of the real thing!

You must mean a model, even if u could buy an engine like that full-sized it would cost u about as much as a house, if not more.

Depending on what gauge u r interested in there is a range of models of such locos from various manufacturers with matching rolling stock.

l suggest u get a copy of the rail magazine, 'Continental Modeller' or 'International Model Rail' which cover all overseas railways including oldtimer US.

Plenty of articles & adverts in there, u r bound to find something to suit. Also advertised u will find rail DVDs which include oldetimer US locos - heritage lines, archive film, etc.. If u can not get the real thing, at least u can get a good DVD.

Good hunting :->