Colin Grant (Andrew Cawley / DC Thomson)

SCOTTISH half-term holidaymakers face a currency lottery when returning their unused euros.

A Sunday Post probe has found that High Street chains are offering widely differing exchange rates to customers with leftover holiday cash.

And, with the tumbling price of the pound following the Brexit vote leading to soaring costs for families heading to the European mainland for a break, some rates offered were described as “disgracefully low.”

Our probe found customers could lose out on as much as £23 when converting €500 back to sterling depending on which shop they went to.

Consumer groups have urged people returning from abroad this autumn to shop around for the best deal.

We contacted several leading currency exchange services to find out what we would be offered for €500.

Our investigation found the Post Office had the worst deal, offering £390.63.

Thomas Cook Travel offered £413.22 for the same amount.

Many Bureau de Change outlets were selling €500 at a cost of around £450-£460.

Emma Coulthurst, from holiday price comparison website TravelSupermarket, said: “Buy-back rates for changing your holiday cash into pounds are notoriously poor.

“There can be a frustrating lack of transparency when you try to compare what you’ll get back.

“Some companies even offer different rates depending on where you live in the country. Where there is a lot of currency exchange competition in an area, it’s likely there will be better rates on offer and the reverse where there isn’t much competition.”

We contacted branches of Debenhams, the Post Office and Thomas Cook in Glasgow, Edinburgh, Aberdeen and Dundee.

Some of the rates even differed between postcodes.

While Debenhams and The Post Office offered the same rates nationwide, Thomas Cook’s varied in different places.

Branches in Aberdeen and Fife offered £393.21 for our euros, while one office in Dundee was willing to pay out £413.22.

We also contacted branches of Sainsbury’s, Asda and Tesco to see what deals we could get.

Our investigation also looked at the return rate for dollars but did not find the same levels of disparity.

Helen Saxon, chief analyst at MoneySavingExpert.com, said: “Rates for selling back unused holiday currency are often disgracefully low. The best way to avoid poor buy-back exchange rates is to try and estimate how much currency you’ll need for the trip, so you don’t have lots left over when you get home.”

A Post Office spokesperson said it aimed to keep “rates as competitive as possible so that we compare favourably with all our competitors”.

The other firms declined to comment.