I saw a cleaning product on the shelf, noted the price on the shelf-edge label and went to the till. The item was then priced somewhat higher. I demanded the lower price and the shop refused. I left, rang trading standards and was informed that the shop was within it's rights to refuse to sell to me at the lower price.
I would check with your local trading standards office (usually accessible via citizens advice bureau) and seek their opinion.
I think we are all singing from the same hymn sheet. I think BenidormHereICome (BHIC ) described the process perfectly and Greenshoes very succinctly.
As the transaction wasn't completed (no acceptance of the offer) there's no contract. WSH do seem to have helped the bank process the "adjustment to the client's available balance".
I still question why the bank (clearly) needs such help. If money CAN be extracted electronically and almost instantly why cannot the abort of the initial request be processed with equal speed ?