“Israel changes it’s barcode prefix to avoid products being boycotted!”
This is untrue, all countries have what’s known as a Global Trade Item Number (GTIN) or barcode prefix and it cannot be changed at will. The purpose of the GTIN barcode prefix is to indicate the country where the company selling the product is registered, NOT where the product has been grown or made.
This means only products sold by a company registered in Israel will have the Israeli GTIN barcode prefix 729. Likewise, if a UK registered company sold a product made/grown in Israel it would show the UK GTIN barcode prefix (500-509) instead.
For example, this bottle of shampoo clearly indicates that it was made in the UK, however when we look at the barcode the GTIN prefix is for the US.

The only way we can know for sure if goods or produce are Israeli is by checking the label for “made in Israel” or “grown in Israel”. It’s important that when engaging in boycotting activity that we understand what the GTIN barcode prefix indicates. This will help us to avoid spreading misinformation and allow us to focus our attention on companies and products that are made in Israel.
Unclear Labelling: What To Do
It is a legal requirement that all fresh fruit and vegetables include the country of origin. This must be visible on the packaging or if produce is loose there should be clear indication on the product display shelf, or a produce label should be affixed to each individual item.
If you notice unclear labelling on fresh produce in your local supermarket you should make a complaint to customer services. You can then follow up that complaint by reporting to your local Trading Standards office. When filing a complaint with the Trading Standards office ask that they keep you updated on the actions that they’ll take and ask them to visit the store directly. If the store continues to conceal the country-of-origin information report them to Trading Standards again