No not quite. Companies will put in their own t+c's, allowing for mistakes, and to actually prove you have "loss of bargain" you need to be able to prove that the price that was offered could have been inferred as genuine. An example recently is a chair on the M+S website that was on sale for £1 in a certain colour. Other colours were over £1k. despite accepting orders, and taking £1 from people, they have cancelled without recourse.
I agree that you have to be sensible though, as obviously mistakes are not usually sustainable.