Housing affordability has deteriorated to the point where some regional housing markets are close to, or in the case of London equal to, the crisis levels in the end of the 1980s boom. This is the situation when affordability is measured by the price:earnings ratio, but the broader measure - which includes interest rates - shows affordability only a little worse than the long-run average. <p></p><p>This is likely to apply a brake on the market, but only a significant interest rate rise would lead to a serious fall in house prices in the south. </p><p>The HBF survey shows that visitors are up on a year ago, and reservations well up - April's balance of +29% is the best since September 1999.</p><p> But the supply side is still struggling. </p><p>Government figures for the first quarter show that seasonally adjusted starts in the private sector, although up 7% on the previous three months, are down 6% on last year. NHBC applications in the first three months were down 8%.</p><p><b><br> <b>HBF Monthly Survey Summary Results</b></b><br><b><br> <b>Activity in the month compared with the same month a year ago (balance*)</b></b></p><p> &amp; <b>Jan</b> <b>Feb</b> <b>Mar</b> <b>Apr</b></p><p><br> Site visitors -4 +5 +12 +5</p><p><br> Net reservations +7 +28 …