On weekdays (Mon-Fri London time) the interbank exchange rate is applied to all transactions with exception to Thai Baht (THB) and Ukrainian Hryvnia (UAH) where there's a 1% markup on top of the interbank rate.
If you exchange currencies on weekdays (Mon-Fri London time) you will receive the interbank exchange rate without any markup on all currencies except for THB and UAH where there's a 1% markup. In addition a 0.5% fee will apply to anything above €1,000 per month.
On weekends (Sat-Sun London time) the provided rates are fixed to protect against fluctuations. Additionally, there will be a 1% markup on all currencies except THB and UAH where there will be 2% markup.