Remortgage help.

Phil01_2

Hello, I wonder if anyone can help with some information. We are looking to borrow an additional 60,000 on a mortgage of 106,000 to do an extension, but my bank are only prepared to lend an additional 46,000 as the value of our house has fallen from 190,000 at the end of 2007. Not had the house valued again since but have assumed that value will now be closer to 170,000 due to the drop in the market and the bank will only lend 90% of the current value of the house. Will this be the case with all lenders and does anyone have any suggestions as to how we would be able to increase our mortgage by 60,000?
Thanks in advance.