dependants-you're responsible financially for someone else, so suppose that this might be depremental
the credit check will show if you have a mortgage, they may ask for a mortgage statement as proof
reason for loan does effect the decision
it could be that you are 'over-committed', when the app is processed it will tot up the credit that you have and calculate if you can reasonably afford the credit. Depending on the criterea of the loan application you may not have scored enough 'points'. The less the APR, the higher score is needed, hence, high APR are usually available to low credit scorers. May well be that you just don't have enough credit history to check, I've known of people who has never had credit, always paid their bills on time and always worked being turned down for credit.
You can get in touch with Experian/Equafax and ask to see your credit file or you can access it online. It will cost you either way but I'm not sure how much.
It's nice to be back......