A bank would look at far more than just your salary. They'd need to know how much credit you already have available (e.g. through such things as credit cards) and what your monthly outgoings are on such things as mortgage repayments or rent..
Abbey currently quote monthly repayments of around �300 for a loan of �23000 over 8 years. If you can convince them that you'll have this amount spare each month, you stand a chance of getting a loan. �300 per month equates to �3600 per annum but to get that amount in your pocket after deduction of tax & National Insurance, you actually have to earn nearly �5000 per year. So, the bank needs to be certain that you'd still be able to meet all of your existing outgoings if your employer was to suddenly cut your salary by �5000p.a. Similarly, if you were hoping to repay the loan over 5 years, the bank would need to be satisfied that you could still meet your existing commitments if your employer was suddenly to reduce your salary by �7000p.a.
Chris