Uninstalled an addon and now unable to reach site?

Error message:
Fatal error: Block::getInstance() [<a href='block.getinstance'>block.getinstance</a>]: The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "BlogPostsBlockController" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition in /home/sites/mellingparishcouncil.org/public_html/updates/concrete5.5.1/concrete/models/block.php on line 329

Any assistance appreciated.