Having had a chat with GoCardless:
i've just spoken to our BD team and they've asked that, if you (and anyone else who would like a Blesta integration) could email in to help@gocardless.com stating you want this module I can forward these on and see if we can convince them to develop one.
From my perspective, what would be ideal, is Blesta and GoCardless working together to create a module which is actually supported, and properly supports Direct Debit payments in the UK (And soon across the whole of Europe).