Banking in Sri Lanka is not difficult but for some country's credit cards are working only for one time and in second time it could be found to be locked by the original bank. Therefore visitors from France (I dont know what are other countries exactly) prior to visit Sri Lanka must get the authority from your French bank to use it in Sri Lanka otherwise you will be in a problem when using ATM machines. In such cases bank will help to involve with card centers to withdraw some money for you on your request (it takes a lot of interest.) In cases of French only speaking visitors must know Sri Lankan bank people speak English only. Hence, if a problem occurs, it will be difficult to discuss with bank and you will go helpless.
Anyway, if you are going to do all of your transaction with credit cards within Sri Lanka, it is advisable to keep some extra euro notes in your pocket.