EVERY day customers come into the busy Cash Converters store in Glasgow city centre to buy and sell.

Some are looking for £30 for an old mobile phone, others are more in need.

"The worst one I had was a guy who came in and had a CD," remembers Harry Harrison, general manager of the Renfield Street shop.

"We sell CDs for 20p, we buy them for 10p. We need to see some ID when we're buying from customers and when I asked if he had any he didn't. He came back two hours later with his ID and the CD to get 10p. That's probably the least amount I've ever handed out.

"I'll tell you how desperate people are for money; they'll phone up and say, 'I've got a router', which you get for free from the broadband provider. We don't buy them because you get them for nothing. One guy said, 'Will you not even give me £2?' We've done it the odd time."

This is no ordinary store and the customer base couldn't be more diverse. Harry describes it as "extreme retail", the business model that offers cash advances and personal loans as well as pawnbroking and the sale of second-hand goods.

It takes centre stage in the new three-part BBC Scotland series Cashing In, starting tonight.

Wander round the Glasgow shop and it is a treasure trove of electronic goods, as well as more unusual items. A row of rainbow-coloured Dyson vacuum cleaners are lined up along one wall, a stand nearby houses fishing rods of all shapes and sizes and in the middle of the floor is a mobility scooter.

As benefit cuts are more painfully felt in this age of austerity, Cash Converters offers a simple means to get by for and an alternative way to manage their cash.

"You'll get people who are unfortunately drug addicts or alcoholics or have mental health issues, and then you'll get the person who has a Mercedes parked outside and is in buying a telly. It is the most extreme customer base," he says.

"I had a woman in the other day who came in to borrow £125. She needed the money to buy a tyre for her BMW. She was waiting to get paid at the end of the month and came in and pawned her iPad.

"She tried to get an overdraft and her bank wouldn't give her one. She was a middle class lady with a BMW just a couple of years old."

The Renfield Street store, the fourth in the UK, opened 17 years ago. Since Harry joined in 2013 turnover has risen by more than 20% to £900,000, a credit to not just his management style but how staff interact with customers.

The sales team are upbeat and helpful, no-one looks down on customers or judges them and some have developed strong bonds with customers such as Elaine McMath from Maryhill.

Her 27-year-old son Mark suffers from Lowe syndrome, a condition that affects his eyes, brain and kidneys, and she has to get by on Carer's Allowance of less than £65 a week.

In the programme tonight we see her come into the store to sell an old stereo and mini fridge to raise some much-needed cash.

"I use the shop all the time," she says, after getting £10 for the items. "This bit of money will go towards clothes.

"My motto is there's always someone worse off than you."

Ongoing benefit changes means millions of families like Elaine's are facing increasing hardship and have to borrow to survive.

"That is the hardest bit when someone comes in and they are desperate for say even a fiver," says Harry." I remember a young lad coming in looking for money to pay the electricity.

"He comes in all the time, he's a good guy. He wanted a fiver and gave me an SD card. We give SD cards away, we don't buy them. If someone buys a camera we just give them an SD card. I gave him a fiver for it.

"But the guy came back and bought it back, so it wasn't as if he took the mickey out of me."

Harry says the series will open the eyes of many who look down on stores such as Cash Converters. They don't offer loans at extortionate rates and when people choose buy back - selling an item to the store with the option of buying it back and paying a small interest charge - they receive a minimal amount.

He explains: "We are now trying to help people by not giving them as much as they want. Say someone has a £200 phone and you'll ask, 'How much do you want to borrow?'

"They'll say they want the maximum but if they get that they'll have to pay quite a bit back. We ask if they can afford to pay that back.

"That has changed the way our customers think. They now know we want them to come back and get their stuff. We don't want it to sit on the shelves."

One staff member describes his job as a cross between a social worker and auditioning for the Jeremy Kyle Show, a television programme one customer has appeared in.

"A guy came in who was exchanging a phone. I said you need ID, and he gave me a letter from the Jeremy Kyle Show," says Harry.

"I said, 'No way, have you been on the Jeremy Kyle Show?' He goes, 'It's going to be shown in a couple of weeks. My missus was having an affair with the neighbour next door. I set up a webcam in my bedroom to catch them.

"Then he gets his phone out to show me the video."

Staff work closely with the police to ensure stolen goods aren't passed on to the store and one unlucky customer is taken away by enforcement officers during tonight's programme.

"We help the police a lot. If something has been stolen and we have purchased it we tell them straight away. The person gets the goods back, it goes to court and we try and get the money back.

"I think we do a good job of helping the police get these people."

Cashing In, BBC One, 9pm

Read her Glesgabox TV review here