If you haven't been lucky enough to find one of the new £5 notes that's worth a fortune, there's no need to give up hope.
Polymer notes with serial numbers beginning AA01 are being snapped up by collectors and have been selling for hundreds of pounds. In the next year or so, polymer £10 notes will start appearing and no doubt attract similar prices.
But they're not the only British currency in wide circulation to be worth more than their face value - so it's worth checking the contents of your purse.
According to the Manchester Evening News, some 50p coins, for example, are selling for as much as £3,000, with plenty more worth £20.
So what should you be looking out for?
London Olympic 50p piece - £3,000
The 50p pieces issued for the 2012 Olympic Games come in one of 29 different designs. While most are worth no more than their face value, one design featured water passing over a swimmer's face, before it was replaced by a version making the swimmer more visible. As a result, the early version is worth as much as £3,000.
1983 'New Pence' 2p piece - £650
In 1982, the words 'New Pence' on the 2p piece were replaced by the words 'Two Pence'. However, a year later, the Royal Mint accidentally produced a small number with the old wording. While they went into special collectors' sets, some may have made their way into circulation, and could be worth up to £650.
Kew Gardens 50p piece - £50
Around 210,000 special edition 50p pieces with Kew Gardens' pagoda on the back were released in 2009 - far fewer than the usual five million or so. Because of their rarity, they are currently changing hands for around £50.
EC commemorative 50p piece - £20
Only 109,000 of these commemorative coins were issued, celebrating the British presidency of the council of Europe, in 1992 and 1993. They are now worth around £20.
Guy Fawkes £2 piece - £16
Another production mistake, some of the Guy Fawkes £2 coins released in 2005 bore the words 'Pemember, Pemember the Fifth of November' instead of the correct words of the rhyme - and are worth eight times their face value as a result.
Charles Dickens £2 piece - £8
Commemorating the 200th anniversary of the birth of Charles Dickens, these coins were released in 2012. It's their rarity - only 20,000 were issued - that makes them worth around £16.
Mary Rose £2 piece - £6
This was released by the Royal Mint in 2011 in a limited edition of 20,000 to mark the 500th anniversary of the sinking of the Mary Rose. It's worth around £6.
King James Bible £2 piece - £6
Marking the 400th anniversary of the King James Bible, the 20,000 limited edition of this coin makes it worth £6.
If you're lucky enough to find one of these coins, you can check what they're selling for on eBay or through ChangeChecker. Alternatively, there are plenty of specialist coin dealers around the country who will make sure you've really got what you think you have, and advise you on its value.