Johnni,

The 5k is just the maximum they'll allow for anyone with the same account as yours. It doesn't mean you're pre-approved for that unfortunately. To be honest with you, a leap to £4000 from £250 is huge, and I can't see that you'd get that amount unless you had wages going in each month to clear that amount. In my experience they calculate your overdraft limit by what amount you go back into credit each month. If your wages don't cover your overdraft (and they'd have to be great wages to do that!) you won't get an amount like that. If you have online banking you can look up your pre-approved offers on the left of the balances screen. If you don't, go in an see a personal banker and ask them what you're entitled to. When I worked for Barclays they'd give you 'limits' based on how you ran your account, which meant they'd know what you were allowed before you applied. They also have limits for Barclayloan which means they can tell you if you'd get your loan. It won't take a credit search, but I'd definitely do that rather than just apply.

You need to think about if you could afford to pay back a 4k overdraft and have the discipline to clear it, you're not meant to have an overdraft and go right to your limit each month. Could a loan from another company be an option, or is it necessary? You could get a copy of your credit report for free from creditexpert which would see if it's worth looking elsewhere.

Good luck, and sorry this is long-winded, hope it's helped you!