Lenders Resimac, FirsMac, Mortgage Ezy and Mortgage Port have agreed to work with One Big Switch under its group discount plan, according to today's Australian Financial Review.The AFR said people in South Australia who have registered with One Big Switch have been told they will be eligible for discounts of between 10 and 40 basis points off the lowest available variable rates offered by those lenders.FirstMac's online brand, loans.com.au, offers a home loan with a variable rate of 6.69 per cent.One Big Switch said it would announce group discounts in all other states within a month.One Big Switch has received 40,000 registrations. It will earn a 50 basis points commission on any loan that takes advantage of the group discount and pass $250 of that onto Choice, which has promoted the business.The four lenders receive their funding through a mix of securitisation issues and wholesale lending from groups such as ING Direct, National Australia Bank's Advantedge division, Bendigo and Adelaide Bank and, to a lesser degree, Commonwealth Bank and Westpac.It will be interesting to see how big banks respond to these small lenders trying to lure their borrowers with discounts or 10 to 40 basis points. Westpac yesterday announced that it would offer discounts of up to 80 basis points of its standard variable rate and Commonwealth Bank has been offering discounts of up to 100 basis points for some months.