@Gixer
Most of the suppliers I've been with prefer you to be at least a month's direct debit worth in credit by around October. Avro are probably averaging a winter's usage for your direct debit to avoid a negative balance - so I would argue that this small and temporary increase is in your best interest.
As I've recently switched to Green, I've hardly built up any credit. But when I get my refund back from my old supplier, I plan to pay this to Green so I am almost immediately a month's DD in credit. I could keep the refund and stomach a likely increase in direct debit for about 6 months, but it's not worth the hassle.
One thing I don't like with Green, is that to log in to their website portal, they email you a one-time "Magic Link" you need to click on. You don't have the option to set a password, so this Magic Link is always needed unless you use their app on your phone/tablet. I don't want an app just for the sake of being able to 'conveniently' manage my gas and electric!