heres a question, if the shop had not given you the snake but you came home and gave spread mites to your reptiles ( yes you can transfer them via clothes etc) how would you have treated them?? mites can come from many sources, so you should really have cash available to treat your animals for anything that may come about, even if you have to put money away each month / week, if you cant afford to do this you maybe have to ask yourself the question, can you afford them? as the upkeep of these animals includes vet and treatment costs not just heat and food.
In the mean time you will have to find the cash from somwhere to treat everything, there may only have been a few visible mites but you wont be able to see their eggs. and if not treated properly you will soon see more......
over here we use either ardap, frontline or callingtons, not sure what the best treatment available over there is or if its the same as here.
soap and water wont do at all it will not kill the eggs
sorry to be blunt.