I rarely, if ever pay using cash. I have a smart card that charges me 24 hours after travel for my train journey. I pre-buy QR coded bus tickets (day tickets) online, so I don't get that much change given to me.
But if there is an establishment that lets me know they prefer cash, I will accommodate that - indeed, this is the case with my hairdresser. I'm not going to be judgemental or accuse them of dodging tax - they operate in a very competitive environment and are definitely not living high on the hog.
Just let me know in advance and I will make the decision based on whether I have any money with me, and/or if there is an ATM nearby if not. What I hate hate hate is going to places that ASSUME you will pay cash and only tell you when coming to pay. And I have - before now - been somewhere where there was no nearby ATM and no prewarning - and offered to pay by bank transfer, which was refused. That's suspicious.
So long as someone doesn't post that utterly pathetic FB/social media post about "paying your hairdresser £50 cash and them using that to buy supplies etc etc".
This obviously involves mythical free business bank accounts that allow people to pay cash in for nothing, and probably them avoiding tax.
Don't. Please, just don't.