The lender first launched the range in January which offers borrowers an overpayment facility of up to 10% each year and the option to apply for repayment holidays.
It has cut the rates its two-year fixed rate deals to offer a 3.89% deal at up to 75% LTV, a 4.59% rate at up to 80% LTV, and a 5.29% product at up to 85% LTV.
All three products are for purchase deals only and come with a £995 fee.
The lender has also cut the rate on its two-year tracker to 2.59%, or Bank of England base rate plus 2.09%.
It comes with a £995 fee and is available for purchases at a maximum 70% LTV.
Northern Rock has also launched several fixed rate and tracker deals, including a three-year fixed rate deal at 4.29% with a £995 fee and available up to 70% LTV.
Six fixed rate deals have been to added to the buy-to-let range with rates from 5.59%.