To ditch old credit cards, or not to ditch? That is the question... but I'm afraid there's no easy answer as to whether you should always close down old cards. Lenders can interpret your actions in different ways.
Some will welcome you keeping the cards open. This is because a long-standing account with a good credit history can help boost your credit score. However, other lenders may take a dim view. Why? Because of concern that you have such a large credit facility already on tap that you might turn it on at any moment (thus impacting your ability to repay them if they grant you a card).
Yet there's an advantage to cancelling you should consider: cancelling them can also mean you're able to bag "new customer"-only offers sooner. For example, you'd have to wait six months to be a 'new' customer to Barclaycard or HSBC, if you'd cancelled an existing card from one of these providers.
You need to weigh up whether you'll ever likely need to use the cards again, or if you'll be applying for future credit elsewhere. Find a full rundown of all pros and cons in Cancel Old Cards.