i'm remortgaging at the moment to get some house improvements done. as far as i know they don't ask what exactly you need the money for (it could be home improvements/holiday/pay off other loans), but this may differ from lender to lender. the list of information the lenders require is something like the following :
6mths bank statement, 3 recent payslips, a utility bill in your name, last P60, a statement of mortgage repayments and outstanding balance, a statement of any other loans and a letter/form from your employer sating salary - although if you're self employed you may need extra info.