I got told sniffily "there's a bike rack outside" when I took my unfolded Brommie into
Evans (yes, that Evans, the bike shop) in Peckham. I decided against making any purchases and continued my journey.
This meant that they lost a massive sale of something or other. Cable end caps maybe. Something like that.
That said, it's entirely the shop's business whether they let bikes in or not. They don't need to make up spurious elf n safety excuses. They can just say "no", to which the cyclist can reply "OK" and go somewhere else.