The July 2008 ComScore numbers for Unique Visitors to UK property portal sites shows that rightmove.co.uk continues to be the most popular site in the UK as it has been for many a year.
What is interesting is that the propertyfinder network (propertyfinder.com, hotproperty.co.uk, and ukpropertyshop.co.uk) reaches a combined (de-duplicated) audience of 1.6m - and ahead of findaproperty.co.uk and primelocation.com. If you break the propertyfinder.com network into its 3 sites - then propertfinder.com had 1.2m UV's, ukpropertyshop.co.uk had 436k UV's, and hotproperty.co.uk 315k UV's.
Anyway you cut it, the "big 4" continue to have the lions share of the UK online real estate market as they have for the last 5+ years. We hear much about new entrants and the free to list, pay to upgrade model, however these site still struggle to match the big 4 in traffic no matter how much they spend on marketing.
Now some of the sites will contest the figures are being wrong and from my time with the REA Group (owners of the Propertyfinder Network), the internal Nielsen NetRatings numbers were always higher, however, putting the absolute numbers to one side and just focusing on the relative numbers, it is clear that the big 4 are entrenched at the top of the rankings and this is very unlikely to change.