When I worked in a bank many years ago we used to read out the words written on every cheque to check that they were correct. We'd also check that there was a payee, the date was correct, that the words and figures agreed and that there was a signature. If we'd come across a cheque using the word quid we'd probably have had to refer it to one of the sub-managers to see if it would be allowed. I'm pretty sure they don't check all cheques these days so you might get away with it without it.