Apply html elements in php statement

Do this instead:

add_post_meta($newpostid, 'name', $formdata['your-first-name'] . ' ' . $formdata['your-last-name']);

This uses PHP string concatenation to add a space; the echo isn’t necessary in in this instance because WP will do it itself, later. You probably can’t force a non-breaking space there, either, since WP will escape all its output.