I'm not too sharp with this whole credit card business. But if I owe say £500 on a credit card A, if I pay that off with credit card B within the time allowed so as not to bay any interest. Can I then the next month use credit card A to repay the £500 now on credit card B. So only having the £500 in any account for no more the 3/4 weeks. Would this avoid any interest at all untill I repaid it in full?