Hi Simon,
I understand what you mean now. I took care of this. In the future, you can do so by checking the text view (in the edit function), and removing any of the junk. But a better practice would be to compose your entries in the editor (or paste into the text view, at least). Pasting into the text view won't bring in images, but you can add these through the media uploader, anyway.
I hope that helps!