Hi there,
First you don’t set a Display Location in the Block Element
Then use the generate_block_element_display filter to set it to display true if the correct conditions are met so something like this:
add_filter( 'generate_block_element_display', function( $display, $element_id ) {
if ( 123 === $element_id && strpos($_SERVER['REQUEST_URI'], 'london') !== false ) {
$display = true;
}
return $display;
}, 10, 2 );
The 123 in the code is the Elements ID – which will need to be changed to match your Block Elements ID.