On a different (but slightly related topic) Evans Waterloo Cut charged me:
First visit: two hyperglide pins £0.20
Second visit: two hyperglide pins and a powerlink £3.00
Third visit: two track nuts £0.00

So I'd say that "they'll only charge you if they are a c***" depends entirely on who serves you.

Apart from the inconsistency which I found slightly puzzling I had no issues paying each time.
I did prefer the last however.