An overdraft is a temporary thing - usually ranging from 3 months to a year. In practice, they will in all likelihood renew it (they make money off you when you are overdrawn). Call them asap as just in case they say no (which they are well within their rights to do) it gives you time to go elsewhere.
If you do keep within your facility, they will in all likelihood renew it, but if they don't you need time to open up a new account with another bank - Halifax are rather good and usually match your cuurent facility.