In youre settings you can have limits to how many feedback a buyer must have before they are allowed to bid on your item, and another that bans buyers with X number of negative or unpaid transactions.
Maybe to be found in the seller dashboard 😕
Also make sure you’ve limited your sales to UK mainland only, or you’ll get all sorts of inquiries or worse buyers, from the far east, Russia, Africa and beyond.
I only sell in the UK, because if it goes missing, trying to converse in a language you arent familiar with to claim through or inquire in some other countries postal system is nigh on impossible.