Another potential supplier would be Octopus. We have recently upgraded our PV system which has drastically changed our import/export profile and waiting for our Ecotricity account in the coming days to see how much things have changed, which our solar installer can use for a comparative simulation. Octopus's peak/off peak times aren't as generous as Ecotricity's but lower night rate and 17c export rate looks like it will more than swing the balance.