That will work, at first. It is not a long-term solution, as algorithms and technology will simply evolve to recognize in spite of that. The solution, at least for America, is to remind the feds that they have no constitutional power to use facial recognition, for a similar reason that mass surveillance is unconstitutional. It's a breach of the Fourth Amendment Right to security in persons and papers, I would argue (as is TSA), as well as a violation of the Due Process Clause, because it makes every one a suspect (same issue with fingerprints, DNA, etc.). The bottom line should be that law enforcement has no right to do anything, hold information on you, surveil you, or put you through airport security unless you commit a crime. Quite frankly, there should be no such thing as a "watch list" -- they don't get to make you turn over information or treat you as a suspect (note their use of the term "suspicious behavior" - behaving like a suspect - as a justification) when you have done nothing wrong.

There was a comment I read on another thread about some one who bought about 20 pressure cookers when they were accidentally marked down for a dollar apiece and had the police called on him. Is that really okay? I have also heard that the FBI is notified if you buy more than a certain quantity of fertilizer.

Can a Brit enlighten me as to if there are similar protections or justifications against this technology in England?

As mentioned in another comment, this is the gradual erosion. They say "we want to compromise", get some ground, then push more and "compromise" again to push the line further. Trading liberty for security is a risky game.