You can have up to 10 cards on your account at any one time. You can set individual limits on each card. All cards are subject to the credit limit on the account and your statements will show transactions split by cardholder.
For example if you have £4000 credit limit and spend £500 on one card there will only be £3500 available for use by the other cards or to be drawn down.
It's worth noting that on our rewards club (£199 annual fee) you can have up to 20 cards on your account!