I don't know about the Spitfire, but in the many full size aircraft I've flown, You just maintain attitude with the stick then trim out any force you're holding. Some want to pitch up, some want to pitch down and some have little pitch change. I don't know of any that have a mechanical connection to change trim with flap deployment. The amount of pitch change also depends on speed and a constant correction would be too much at times and not enough at others. The way full size aircraft are flown is to fly the airplane with the stick then make trim changes as necessary to reduce stick force.