Add the following function in your template.php
function THEMENAME_render_block($module, $delta, array $options = array()){
$default_options = array(
'title' => '<none>',
'region' => -1,
);
$options = array_merge($default_options, $options);
$block = db_query('SELECT * FROM {block} WHERE module = :module AND delta = :delta', array(':module' => $module, ':delta' => $delta))->fetchObject();
if($block) {
$block = block_load($module, $delta);
$block->title = $options['title'];
$block->region = $options['region'];
$blocks = array($block);
$rblocks = _block_render_blocks($blocks);
$render_array = _block_get_renderable_array($rblocks);
return drupal_render($render_array);
}
return "";
}
then in your views header render the block like so
<?php print THEMENAME_render_block('<moduleName>', 'delta', array('title' => t('Filter Title'))); ?>
For this you must have views php module enabled if you want to render the block from views header or else you can use tpl file to render the block in the header as @rooby suggested.