The amount you'll be able to borrow will vary between lenders, with factors such as your income and credit history used to determine how much a lender will offer you (if at all).
Before comparing loans, always check your credit history to make sure there are no mistakes and all the information is correct. There are also easy things you can do to improve it if it's not in a great shape. See Check your credit report for free and how to improve your credit score for full help and top tips.
You can then use our loans eligibility calculator to see your chances of acceptance for many lenders. You can then play around with the amount you're looking for, plus the length of time you want to repay it to see how that changes your results.
A longer term will mean lower monthly repayments, however you'll pay more in interest over the course of the loan. Always aim to repay debt as quick as you can, to minimise the cost as much as possible.