Hello there,
I get the following error, which weirdly only gives blank page when using shipping estimator on shopping cart page, so far only United States and Canada upon testing:-

PHP Fatal error: Uncaught TypeError: Unsupported operand types: float + string in /includes/modules/shipping/BigRoyalMail/quote.php:151
Its fine in php 7.x , the issue only occurs on php 8.x . I guess its something to do with rest of world zones. I read on google that it just needs parentheses adding at certain points, but that was for a different system to zencart. I swtiched back to php 7.x for now, trying to suss it out but the code seems to spread over 2 lines that it refers to.