ISP: BT (British Telecom)
Country: United Kingdom
Time of day: Heavy lags from 7pm (GMT+1) which makes the game unplayable, usually stops around 11pm.

No lag during any other time of day or night however I am dreading the coming weekend

Would be good to hear whether SE plan to contact BT to address this issue. I have tried to speak to them but they are a bunch of useless idiots who are convinced that running speedtest proves that this is not a problem on their network