import re
phrase = '5 hampshire road bradford on avon avon dinas powys powys north somerset hampshire avon'
c_except = [r"on\s",r"dinas\s"]
c_out = ["avon", "powys", "somerset","hampshire"]
rx = r"(?<!\b{0})({1})".format(r")(?<!\b".join(c_except), "|".join(c_out))
print(re.sub(rx, "", phrase))