yelenots, can I suggest that you pay a couple of quid and run a credit reference agency report on yourself, someone like Experian? That will tell you if you have any negatives on the credit report for you, which the companies use when rating any applications - and if it's wrong, you can apply to have it corrected.
Some companies however are being a lot more canny now, they will turn down applications if they think that the repayments might cause you to overreach your budget.
Worth having the check done anyway - some years ago mine had wrong information which was affecting my credit rating.