erm, no its not. Because your looking at outliers only. London might be the financial capital of Europe but I hope your not doing maths here.
If you look at their postcode trend tool (click house prices in my area) to get a large enough sample size, then we look at the distrabution you will see its very noisy to begin with, so lets just use a simple trend line, oh whats that, 3-5% drop... oh my.
Reposessions never really went that high either.
Even then not 100% sure I like their data sample, its better to look at land registry sale prices before saying people lost money.
Don't get me wrong, asking price, mortgage amounts etc are really interesting indicators, but they are not a golden source by any stretch.