Hello KM31,
One of the things a potential creditor will look at is how much credit you could access if you wanted to (or if you went mad in Vegas, that kind of thing).
This means that existing accounts will be taken into consideration as they have no way of knowing that you would not choose to use them.
Also, having lots of unused cards exposes you to greater risk of credit card fraud, so leaving accounts open is not a good idea!
You can check your credit rating and see exactly what the card providers see; you can obtain a copy of your credit report from the main credit reference agencies Equifax and Experian.
You might also find this article useful: The secret path to a better credit rating.
I hope that is some help, good luck with it.
Felicity
Felicity King-Evans, deputy editor
felicity.king-evans @ moneysupermarket.com