Do you need quick access to the money?

How untraceable does it need to be?

As some other people have said, you can buy silver or gold. Just make sure places you're buying from aren't going to low ball you with prices when selling it back.

If you want a solid place to hide them, dig a small hole under a concrete floor in your house.

Place the items in a sealed container, ideally you would dig a small diameter hole and go down. Think Pringles tube standing on end, but not as long.

Then concrete back over the top. Make sure the top layer over your item is only a few cm thick to make retrieval easier.

Don't try to hide them in a wall socket or under a floor board. Those are both places that an investigation would search if you ever get arrested for anything.

But nobody is digging up a concrete floor unless they're looking for a body.

You can even hide cash notes like this nowadays as they're no longer made of paper. But I would not recommend storing cash. Get gold or silver as that is more inflation resistant.

If you need it to be untraceable, ideally you would need to take it out of the bank in small amounts every week and then convert it to gold or silver.

If asked, you can claim a gambling habit. Just say you were betting on sports.

Making a large purchase of gold or silver and paying by bank is easily traceable.

Even putting it into crypto is very traceable when buying directly from your bank.

To properly hide it you would need to take out small amounts over a long period of time.

Around £400-£500 a week could be explained with a gambling habit.