I did well last winter on Octopus "savings sessions" managed well over £100 they haven't been signed off this year yet so still waiting to see what will happen.This year we’ve had around £50 rebated by usage reductions when requested. Plus we had half price electric on many Sundays between specified hours. Not possible without the Smart meter.
As for half price, don't get that as on a time of use tariff however the price does go negative for about 15 days a year or so depending on the wind, its great, they pay me to use electricity and pay me to export. just looked back at the figures and that explains why August was so cheap for me, there were several days when my average unit price was minus 1.5p/kWh and export was on top of that.