Potassium/Ammonium Dichromate is already on the "unobtainable" list, although there are sources via ebay. Borax & Boric Acid are no longer available to the general public for domestic use, but both can be obtained from (most) commercial suppliers.
Of the more common chemicals that we use on a regular basis, I suspect Hydroquinone will be the next one to be "banned" - This will most likely be in response to certain ethnic groups that insist on brewing their own skin whitening concoctions and inflicting lasting damage on themselves and others in the process. As with the other chemicals already mentioned, I doubt it will prevent people from advertising & selling via ebay.
I would suggest making a list of all the raw chemicals that you think you might need, consult the current EU REACH list and perhaps start hoarding some of them.
Oh, and if you come across Glycin or Amidol at a reasonable price, please let me know.