is it true that all mortgage lenders (including sub prime)ask for bank statements before they can accept the application.or do some do some ask for other documenttation
Not necessarily. It's usually used for two main reasons - either to prove your address (which can be proved using a credit check, a utility bill or a credit card statement) or to verify your income and outgoings. However, your income can be proven through your payslips and your outgoings only need to be verified if you're borrowing more than is usually lent to people on the same income.
I took out a mortgage with Halifax last year and didn't have to provide any bank statements, even though I had never banked with them before. i just had to show them 3 months wage slips.