Borax occurs naturally in evaporite deposits produced by the repeated evaporation of seasonal lakes. The most commercially important deposits are found in Turkey; Boron, California; and Searles Lake, California. Also, borax has been found at many other locations in the Southwestern United States, the Atacama desert in Chile, newly discovered deposits in Bolivia, and in Tibet and Romania. Borax can also be produced synthetically from other boron compounds.
WIkkipedia

Proper borax is No longer sold on the shelves in the UK. You have to make do with a borax substitute from Dripak.

“Borax Substitute is sodium sesquicarbonate – a mineral compound, with similar pH to borax, making it ideal for cleaning and laundry. It is gentler than Soda Crystals yet stronger than Bicarbonate of Soda.

Using Borax Substitute around the house
Uses Borax Substitute as a:

Multi-purpose cleaner – Mix it with some water to form a paste. This makes it an excellent scouring agent that offers more cleaning power than Bicarbonate of Soda.
A water softener to help keep your washing machine clear of limescale.
To make your own bath salts, simply add some perfume or essential oils and a drop of food colouring to some Borax Substitute.”

That said you can still buy borax from Ebay

Uses

You can use real borax for the above and
Can be used to make a fire retardant spray
To deter moths

More

Borax, washing soda, bicarbonate or all three. What should you use for your cleaning needs? A comparison HERE
See all out #plasticfree cleaning aids HERE