Don't understand why you thought you had to " sort the property out" before informing bank, etc of your mother's death, as the property can't be sorted until other things have been dine.
You should have registered your mother's death, at the time, and you should have informed the bank so that the direct debits for utilities could be paid from your account, which you would have had to have to set up. New contracts for electricity and water will have to be set up in your name..
your mothers account will be frozen, as it should have been when she died, as it is part of the inheritance, and the money cannot be claimed till it is sorted out.
You cannot sell out the property in Spain until the inheritance tax issue has been sorted.
you cannot sell the house to pay the tax which must be paid within 6 months, or interest will be added