Gazza, I used to have a load who paid by standing orders, but they were mostly the military families who've moved on, but I still have three customers who pay this way.
Just let them know that if you're late, and you receive two payments to one clean, you'll refund them when you clean.
It seems weird mind, when you clean a house and then pay the customer (of course you haven't; you've received two payments). One customer joked that he was putting the price up when I paid him.
I clean these accounts calander monthly, and get paid calander monthly. I arrange all payments for the beggining of the month and clean sometime during that month.
The forms are easy; I can't e-mail you one, but if you ask your bank you can get a form and then copy and personalise it to suit your needs.
Just fill it in for the customer to sign and then you post it to their bank.
It does work.