Banks dont "lend on BMV's" they lend on property.
Where I am, banks will lend the lesser of 70 percent of market value, or what you pay for a property, so if you buy "below market", it doesnt matter. They still will not lend more than 70 percent of what you pay, unless it is your sole home, you will live in it, and you have a very good income to support higher mortgage payments
That's sensible lending. Why should they lend more?
BTW, as banks revert to sensible lending, home prices may well head lower, as speculators with limited cash are squeezed out of the market. I want to buy property where and when sensible lending (and lower prices) prevail. That's what I have been doing... buying outside England.