I have just organised a 85% Buy To Let mortgage with UlsterBank in Northern Ireland - @ 5.49% interest-only.
They will lend 85% max for investment property in NI, 80% max if in other parts of UK.
They also use a different set of criteria than most banks when deciding how much they will lend - instead of the traditional "the mortgage repayments cannot be more than 125% of the monthly rental income" rule, they instead take your own disposable income, and add 70% of the monthly rental income to that. Then they apply the usual 35% of total net monthly income rule to your total borrowings and derive the max loan amount from that.