How typical are you? I am also a grey bearded o.a.p - though I have never worn a cap of any sort since the 5th form.
I pay for everything less than £200 with £20 notes. The remaining £10s and £5s are useful for taxis/tips (I don't drive), while almost anyone will take the coins, there seems to be a street collection service.
I don't have an i-phone, I manage with an old Blackberry which has no internet access and is usually switched off. I know how to switch it on, it has a few pre recorded numbers, including RCR.
I don't understand the problem people have with cash, it's hugely convenient, or at least was till last night