VAT online check for United Kingdom

-- HikaShop version -- : 6.5.2

Hello,

I am working on a solution to verify gb vat numbers, documentation here:
https://developer.service.hmrc.gov.uk/api-documentation/docs/api/service/vat-registered-companies-api/2.0

I got that working but the integration with Hikashop is not so smooth. Checking the vat code, here:
\administrator\components\com_hikashop\helpers\vat.php

I see there is integration with the online check using the trigger onBeforeVATOnlineCheck.

I have 2 issues using this approach:

1. Entering a vat number starting with the letters GB.. causes an error, specifically the error:
Your VAT number can not be used with the country you selected. Please select the right country ( CODE: GB) or make sure your VAT starts with XI
To stop that error, I commented out the line 41 in vat.php

if($zone_code=='GB') $zone_code = 'XI';

		$rc = $app->triggerEvent( 'onBeforeVATOnlineCheck', array( &$obj, &$processed, &$vat) );
		if( $processed) {
			return $rc;
		}

		$rc = $app->triggerEvent( 'onBeforeVATOnlineCheck', array( &$obj, &$processed, &$vat) );
		if( $processed) {
			if ( in_array( false, $rc, true ) ) {
				return false;
			}
			elseif ( in_array( true, $rc, true ) ) {
				return true;
			}
		}