Yes, as long as your lender accepts a standing order.
Yonder sends your payment as a standing order, which is a fixed amount on a fixed date. That works well for a fixed-rate mortgage.
If you're on a variable or tracker rate, your lender will almost certainly need a Direct Debit so they can change the amount when rates move. We can't do Direct Debits yet, so this won't work for you at the moment.
Some lenders only accept Direct Debit whatever your rate. Before you set anything up, check with your lender that they'll accept a standing order, and get the details they want you to use: the bank details and reference, and the payee name or bank name if applicable.
It's no problem if your mortgage is with the same bank as your current account, Nationwide for example. They're separate accounts, so we collect from your current account and send the payment on to your mortgage account exactly as we would to any other lender.
We're working on adding Direct Debit support.