add the following hidden elements to the second form:
<input type="hidden" name="OrderRef" id="OrderRef" value="<?php echo((isset($_POST["OrderRef"]))?$_POST["OrderRef"]:""); ?>" />
<input type="hidden" name="firstname" id="firstname" value="<?php echo((isset($_POST["firstname"]))?$_POST["firstname"]:""); ?>" />
<input type="hidden" name="lastname" id="lastname" value="<?php echo((isset($_POST["lastname"]))?$_POST["lastname"]:""); ?>" />
<input type="hidden" name="email" id="email" value="<?php echo((isset($_POST["email"]))?$_POST["email"]:""); ?>" />
<input type="hidden" name="phone" id="phone" value="<?php echo((isset($_POST["phone"]))?$_POST["phone"]:""); ?>" />
<input type="hidden" name="phonetype" id="phonetype" value="<?php echo((isset($_POST["phonetype"]))?$_POST["phonetype"]:""); ?>" />
<input type="hidden" name="fax" id="fax" value="<?php echo((isset($_POST["fax"]))?$_POST["fax"]:""); ?>" />
<input type="hidden" name="street1" id="street1" value="<?php echo((isset($_POST["street1"]))?$_POST["street1"]:""); ?>" />
<input type="hidden" name="street2" id="street2" value="<?php echo((isset($_POST["street2"]))?$_POST["street2"]:""); ?>" />
<input type="hidden" name="city" id="city" value="<?php echo((isset($_POST["city"]))?$_POST["city"]:""); ?>" />
<input type="hidden" name="state_province" id="state_province" value="<?php echo((isset($_POST["state_province"]))?$_POST["state_province"]:""); ?>" />
<input type="hidden" name="postcode" id="postcode" value="<?php echo((isset($_POST["postcode"]))?$_POST["postcode"]:""); ?>" />
<input type="hidden" name="country" id="country" value="<?php echo((isset($_POST["country"]))?$_POST["country"]:""); ?>" />
<input type="hidden" name="shipping_firstname" id="shipping_firstname" value="<?php echo((isset($_POST["shipping_firstname"]))?$_POST["shipping_firstname"]:""); ?>" />
<input type="hidden" name="shipping_lastname" id="shipping_lastname" value="<?php echo((isset($_POST["shipping_lastname"]))?$_POST["shipping_lastname"]:""); ?>" />
<input type="hidden" name="shipping_email" id="shipping_email" value="<?php echo((isset($_POST["shipping_email"]))?$_POST["shipping_email"]:""); ?>" />
<input type="hidden" name="shipping_phone" id="shipping_phone" value="<?php echo((isset($_POST["shipping_phone"]))?$_POST["shipping_phone"]:""); ?>" />
<input type="hidden" name="shipping_phonetype" id="shipping_phonetype" value="<?php echo((isset($_POST["shipping_phonetype"]))?$_POST["shipping_phonetype"]:""); ?>" />
<input type="hidden" name="shipping_phonetype" id="shipping_phonetype" value="<?php echo((isset($_POST["shipping_phonetype"]))?$_POST["shipping_phonetype"]:""); ?>" />
<input type="hidden" name="shipping_fax" id="shipping_fax" value="<?php echo((isset($_POST["shipping_fax"]))?$_POST["shipping_fax"]:""); ?>" />
<input type="hidden" name="shipping_street1" id="shipping_street1" value="<?php echo((isset($_POST["shipping_street1"]))?$_POST["shipping_street1"]:""); ?>" />
<input type="hidden" name="shipping_street2" id="shipping_street2" value="<?php echo((isset($_POST["shipping_street2"]))?$_POST["shipping_street2"]:""); ?>" />
<input type="hidden" name="shipping_city" id="shipping_city" value="<?php echo((isset($_POST["shipping_city"]))?$_POST["shipping_city"]:""); ?>" />
<input type="hidden" name="shipping_state_province" id="shipping_state_province" value="<?php echo((isset($_POST["shipping_state_province"]))?$_POST["shipping_state_province"]:""); ?>" />
<input type="hidden" name="shipping_postcode" id="shipping_postcode" value="<?php echo((isset($_POST["shipping_postcode"]))?$_POST["shipping_postcode"]:""); ?>" />
<input type="hidden" name="shipping_country" id="shipping_country" value="<?php echo((isset($_POST["shipping_country"]))?$_POST["shipping_country"]:""); ?>" />