Phil, I've solved the issue now I had to alter the following file:
smart_search_customer_44.tpl
{*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
| Smart Search :: alteredCart.com
| All code developed by Bill Brewer
| Copyright (c)2007-2010 alteredCart
| Bill Brewer <bill@alteredcart.com>
| All rights reserved.
| This code is licensed for use on a single server.
| This code is licensed for use by the original purchaser only.
| Full license ::
www.alteredcart.com/license.php
|-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*}
<div class="search">
<div class="valign-middle">
<form method="get" action="_search.php" name="_search">
<input type="hidden" name="page" value="1" />
{strip}
<input type="text" name="q" class="text{if not $search_prefilled.substring} default-value{/if}" value="{$search_prefilled.substring|default:$lng.l bl_search|escape}" />
{include file="customer/buttons/button.tpl" type="input" style="image"}
{/strip}
</form>
</div>
</div>
to the following:
{*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
| Smart Search :: alteredCart.com
| All code developed by Bill Brewer
| Copyright (c)2007-2010 alteredCart
| Bill Brewer <bill@alteredcart.com>
| All rights reserved.
| This code is licensed for use on a single server.
| This code is licensed for use by the original purchaser only.
| Full license ::
www.alteredcart.com/license.php
|-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*}
<div class="search">
<div class="valign-middle">
<form method="get" action="_search.php" name="_search">
<input type="hidden" name="page" value="1" />
{strip}
<input type="text" name="posted_data[substring]" class="text" value="{$lng.lbl_search}" onblur="if(this.value=='') this.value='{$lng.lbl_search}';" onfocus="if(this.value=='{$lng.lbl_search}') this.value='';" autocomplete="off" onKeyUp="ajax_showOptions(this,'getProduct',event) " onBlur="this.form.submit();" />
{include file="customer/buttons/button.tpl" type="input" style="image"}
{/strip}
</form>
</div>
</div>
Thanks for your help with this.