I know they've updated the site fairly recently but there are a few other features that I reckon would be useful. One is a favourites list, which requires no explanation. And another is an 'un'-favourites list. This would be particularly useful when looking for any car in a price range. If you've seen a shed once and know you don't want it it'd be useful to take it out from future searches. You can always add it back in if you wish.
Any other ideas?