I used to work for Abbey many moons ago and I'm sure they need to give you a LOT more notice than 3 days. I can't remember how long you normally get but I would think it's about a month.
Can you speak to the Banking Ombudsman to see what they say, or even just the Halifax complaints department? I know it probably won't change your mind about switching banks but it might let them know they can't get away with doing that.