For the error side of it, I use the form validation extension. You can either leave the validation message next to the relevant form field or put them at the top of the form. For the success message, I get the UE to redirect to the same page that has the email form on it (set in the wizard) but add ?email=success after the page url
contact.php?email=success 
Then add a PHP block above your success message;
<?php if(isset($_GET['email']) && $_GET['email'] == "success") { ?>
and one below it;
<?php } ?>
<?php if(isset($_GET['email']) && $_GET['email'] == "success") { ?> <p>Thank you</p>
<p>Your email has been sent to Strata Medical where one of the team will contact you if it is needed.</p>
<?php } ?>
