In the UK, providers of loans and credit, share information with 3 credit reference agencies:-
Experian
Equifax
CallCredit
I suggest that you contact each agency and for £2.00 you can obtain a copy of your credit file (statutory report) and see what is being passed to those who assess you for loans/credit.
http://www.experian.co.uk/downloads/consumer/Stat-App-Form.pdf
https://www.econsumer.equifax.co.uk/consumer/uk/order.ehtml?prod_cd=UKSCR
http://www.callcredit.co.uk/consumer-solutions/your-credit-report/statutory-credit-report
If any information held is not accurate, you may challenge it and the data shown may be amended.
You also have the right to put a note on your file (Notice Of Correction) to explain any relevant circumstances that may have adversely affected the record. Once on your file, a N.O.C. must be read by any prospective lender before making a decision.
Also by knowing what is on your credit file it may help if you are "up front" with any less than satisfactory account payment history and offer a coherent explanation.
If you have any joint financial commitment with a partner - s/he ought to obtain a copy of his/her credit file as well.
If you do have an existing and good relationship with a financial company e.g. bank, building society, start there. Also if you have a good record with a credit card or store card company, check if they offer loans.
You say that you have means to repay the loan from another source. It may help if you can get that confirmed in writing by say a solicitor or the pension provider - to show to any prospective lender.
There are companies out there that will lend to those with a poor credit history but usually the perception of the "potential risk" will be factored into the terms offered and more likely, the APR% charged.
Be advised also that as you seek credit, a record will be made on your credit file each time someone "searches" it. Searches are, I think, held for 12 months on your file and may also affect any current application lending decision. So don't go firing off applications to all and sundry.