The standard MagSafe charger is identical for US and UK (or anywhere else in the world). All you need is the three-pin adapter to replace the "duck head".
This is available as part of the World Travel Pack, which should be available from any Apple Store.
The standard charger accepts input of 100 to 240V AC, 50-60Hz, which comfortably covers most of the world. If you look carefully, this information is printed on the charger body (in light grey on white!).
If the adapter you're using is behaving as you say, stop using it. You can temporarily use a standard radio/CD player lead (the figure-of-eight connector) plugged directly into the charger after removing the US plug;
That doesn't earth the case though, so some static buildup is possible.
Obtain the correct Adaptor as soon as possible.