Well....
If you are coming with the standard European plug, the one with two pins (unlike the Israeli ones with three pins), you will do just fine without an adapter. All you need is some sharp item with which you can push against the earth socket (the third socket) in the wall. The socket is often covered with a piece of plastic, which, once pushed, allows you to connect a standard European plug to the British socket. This is not necessarily a smart idea, and not being careful might kill you. Still, this works just fine if you know what you are doing.
