Magento Payment Method Drop Down Menu - magento

Question

I am trying to change the payment method radio buttons to a drop down menu.
/app/design/frontend/default/modern/template/checkout/onepage/payment/methods.phtml
This method below works to a degree but while Sagepay processes the order via the radio buttons, it doesn't seem to process successfully when on the drop down menu.
Please could you take a look and let me know what needs to be called? Many thanks in advance!
<dl class="sp-methods" id="checkout-payment-method-load">
<?php
$methods = $this->getMethods();
$oneMethod = count($methods) <= 1;
?>
<?php
$txtArr = array();
$txt ="<select name='payment[method]' onchange='payment.switchMethod(this.value)'>";
foreach ($methods as $_method):
$_code = $_method->getCode();
?>
<!-- <dt>-->
<?php $txt = $txt."<option value='".$_code."' id='p_method_".$_code."'>".$this->htmlEscape($_method->getTitle())."</option>" ?>
<?php if(!$oneMethod): ?>
<!--<input id="p_method_<?php echo $_code ?>" value="<?php echo $_code ?>" type="radio" name="payment[method]" title="<?php echo $this->htmlEscape($_method->getTitle()) ?>" onclick="payment.switchMethod('<?php echo $_code ?>')"<?php if($this->getSelectedMethodCode()==$_code): ?> checked="checked"<?php endif; ?> class="radio" />-->
<?php else: ?>
<!--<span class="no-display"><input id="p_method_<?php echo $_code ?>" value="<?php echo $_code ?>" type="radio" name="payment[method]" checked="checked" class="radio" /></span>-->
<?php $oneMethod = $_code; ?>
<?php endif; ?>
<!-- <label for="p_method_<?php echo $_code ?>"><?php echo $this->escapeHtml($this->getMethodTitle($_method)) ?> <?php echo $this->getMethodLabelAfterHtml($_method) ?></label>-->
<!--</dt>-->
<?php if ($html = $this->getPaymentMethodFormHtml($_method)): ?>
<!-- <dd>-->
<?php //echo $html; ?>
<!--</dd>-->
<?php $txtArr[] = $html;?>
<?php endif; ?>
<?php endforeach; ?>
<?php $txt = $txt."</select>" ?>
<dt>
<?php echo $txt;?>
</dt>
<?php for($i=0;$i<count($txtArr);$i++){?>
<dt><?php echo $txtArr[$i];?></dt>
<?php } ?>
</dl>
<?php echo $this->getChildChildHtml('additional'); ?>
<script type="text/javascript">
//<![CDATA[
<?php echo $this->getChildChildHtml('scripts'); ?>
payment.init();
<?php if (is_string($oneMethod)): ?>
payment.switchMethod('<?php echo $oneMethod ?>');
<?php endif; ?>
//]]>
</script>