The US system used in houses has 3 wires with 180 electrical degrees between them. Black and red are hot, and the white is a neutral conductor that gets connected to earth ONLY where the mains first come into the house.
Voltage from red to white is 120V, voltage from black to white is 120V and voltage from black to red is 240V.
From what little I know about the UK power system, you might not be able to do a direct connection. A transformer would need to provide that exact configuration in order to work properly. In addition, although the difference between the 50Hz in the UK and the 60Hz in the US shouldn't worry the heating elements, it might drive the fan, clock, and electronics completely batty.
Also, you may find that trying to figure a connection out might give the insurance folks a reason to deny a fire claim in the unfortunate case of something bad happening as the oven was not installed per the manufacturer's installation instructions.
I had a somewhat similar situation where someone wanted to install a 220V 50Hz machine that they saw in the Netherlands in the US. It was such a pain to make it work, get the Permits, get it approved and get it blessed by the insurance compaines that the idea was eventually canned.
