Well they only have 1/6 of the UK credit card market by volume.
10.4m Barclaycards: https://en.wikipedia.org/wiki/Barclaycard
60m credit cards: http://uk.creditcards.com/credit-card-news/uk-britain-credit-debit-card-statistics-international.php
So I’m doubtful.
Edit, it can’t be true at 100% of credit card spend is 1/3 of debit card spend:
There were 2.6 billion debit card transactions amounting to £110.8 billion in Q3 2015.19
The above figure compares with 2.3 billion debit card transactions amounting to £100.8 billion in Q3 2014.27
Credit card transactions numbered 798 million in Q3 2015, amounting to £45.9 billion, up from 778 million transactions worth £45.2 billion in the previous quarter.19
So they have 1/6 cards of a £45.9b CC market, but £110.8b were spent on debit cards….