I have the bike bins mentioned above: they are really useful, but they cannot be locked to the pannier frame with the key supplied. The lock only locks the pannier lid shut; to lock them to my bike I thread a cable lock through the handles. I bought mine from the makers at a decent discount because they were 'second quality'. I cannot find any fault with them at all, so their quality control standards must be very high indeed. The bins are very quick to fit and remove, and the shiny surface easily takes high-visibility tape. They have a great flat top for strapping on other articles, and are weatherproof.
They are an excellent piece of design, with the only drawback being that they make a slight drumming noise when empty. This is exaggerated on my bike as it is a trike and the panniers are close to my head, so a rider of a conventional bike would probably not notice this.