Where did the Plymouth Brethren go?

Back in the day when my town had a reasonably broad retail base there was an artist materials and drawing supply shop. I used to buy my pens and Inks there, it was one of the few locations you could buy Higgens drawing ink.  Our government has deliberately extinguished smaller retail enterprises through such means as the Universal Business Rate in order to extract greater revenue from such concerns as betting shops, coffee house franchises and mobile phone shops because such concerns have much higher margins than traditional retail. One effect of this would seem to be the virtual disappearance of the local Plymouth Brethren population, that used to be a visible presence in my locale. Plymouth Brethren being beyond the pale of the normal standards of conformity would like many such groups often have their own businesses, the art supply shop being one such example. I wonder where they've gone?