You can tell a lot of work went into this. They even did a good job finding lookalikes for the background characters. The obvious Britishness takes away from it, though.
While the tiny, boxy cars and constant cloud cover doesn't take much away from this short, it just feels wrong on a very fundamental level. The Simpsons are very very American, in fact almost a meditation on the nature of American life. Nearly everything about the show would have to be changed if it were set in England. I mean, can you really imagine Homer with a British accent?
Meh, I just see it as imitation being the sincerest form of flattery. And while I agree that Simpsons is uniquely American, it is interesting to ponder what the show would be like if it was made in other countries. Especially Britain.