If you want to 100% direct debit you need to get a deal where you can sign customers up. I believe gocardless is about £200 to do that, if you are computer savvy (Excel especially) you can get a much better deal. I'm with smart debit. It takes me about an hour a week to process about 400 direct debits manually, four hours to do 1500 - 2000 per month. It's not for the faint hearted but I pay 1/2 what I would on gocardless.
Being able to sign customers up over the phone, even if they have no email address, is worth its weight in gold especially during covid.
I have customers who I've cleaned for 20 years - always paid cash or cheque - now direct debit after a two minute phone call.