I had exactly the same thing the other week.
Tap drips, replace washer, tap wont budge, pipe through wall does budge (came off)
Re make to stop cock, stop cocks so corroded it leaks through handle. Repalce stop cock. Had to maek new mount to hold outside tap to wall.
I had to use some plastic stuff as the kitchen untis are fitted etc, and the palstic stuff was a lot better to work with then I expected, diddnt feel like a bodge.
Good luck.
