hi pandabean..
think your questions are already answered.. it is difficuilt to see from the birch picture wether it is downy or silver, or even a hybrid but the advice about looking at the crown rings true, probably the best winter recognition, in spring the twigs of the downy will have a soft downy feel at the tip and new growth has a reddish colour unlike the silver...
another way of telling the difference in the winter is to look at the base of the tree... especially in older trees the bark of the silver birch becomes fissured and breaks into rectangular plates this is not so with the downy..
just for future help if you return when the tree is in leaf the big difference is that the downy has a much rounder leaf at the base where as the silver leaf has more of a triangular shape to it and is more pointed, these trees often grow alongside of each other, so return in the spring and see the difference, then note all other differing features for easier future winter recognition..
tree 2 is beech (fagus sylvatica) there are different species of these too, but this looks to have the smooth grey bark of the common beech, just check it hasnt got purple leaves in spring, wich would make it a purple beech..
plant 3 looks to me to be rhodedendron but a close inspection could reveal otherwise..
all the best..
NR