UK Plates:
Okay so we have our standard... Which either have no border, a black border. Or have a GB Euro thing. They used to go something like: R789 DOJ, R- is to represent the year ('98 i believe?). On the new style it goes like this: OY09 NWZ, OY- the area which you got it from, in this case my Clio which came from near oxford. 09 is march 2009-september 2009. if it was '59' this would be sept 09- march 10. Anyway as for "temp plates" We just have dealer plates.
Dealer plates allow an un-registered car to be driven on the roads, over here cars cannot be sold unless they are registered IIRC.
Example of UK plates: (google image search ftw)
Heres something an image search returned on UK plates:
As above you can see the diplomat plates. Living near a housing estate full of yanks i see alot of these