I've lived in the UK all my life, but since I have got relatively few shared taxis in my life, I don't have that much experience of what the social norms are for tipping.
I almost always tip roughly 10% (to nearest pound, occasionally to nearest 50p as long as that's MORE than 10%), just because that's what my parents taught me.
Is tipping required? Expected? A bonus?
I occasionally don't tip - would that reflect badly on me or would the driver not think anything of it?
When people do tip, how much is the norm?