I work for first choice, and the buy back causes us many problems in different ways.
We have a sign up saying its included in all transactions, and to please say if you dont want it.
There was one occasion where we hadnt included it automatically and a customer came back in and was very angry that it hadnt been included becuase they lost so much on the different rates you get when you bring back. The rates to bring back currency are different in every exchange bureau, and you always loose out on the rate. With the buy back included, you dont.
If there is the slightest chance you will be bringing back any currency, then the buy back is a great thing as it does save you money, theres no catch to it.
This is an example of what the buy back can save you:
100 euros at a rate of 1.19 =£84.04 plus the £3.50 buy back = £87.54
becuase of the different rates, if you were to bring back 100 euros, the rate is 1.56, so you only get back £63.72 a differnce/loss of £20.32
So if you came back with only 20 euros, with the buy back included you'd get £16.81 back, without it, £12.75 a saving of £4.06
However, if you know you won't be bringing anything back, then simply say its not required.
With regards to exchange rates, the rates that we get through are lower than some competitors, however we do price match, so if a better rate is seen elsewhere, then simply tell the cashier and they will match.
We dont charge commission on anything except sterling travellers cheques, which is a 3% charge. We can't add commission onto a transaction or anything like that. Everything else is commission free. We dont charge for using cards to pay for money, the amount you see on the chip and pin machine is the amount we charge. However, some banks do charge for using a visa debit card for purchasing money. I'm with TSB and have been charge before myself. its different with different banks. Some charge a % of the amount you have purchased, some are a flat fee. You just need to check with your bank if you will be charged for using a debit card to purchase money. My understanding is, if your card is a maestro switch type, then there are no charges, its only VISA debit that charge. And remember, its the banks charges, not ours.
I hope this answers some questions of how things work.