We use iSupply (just sent in a reading) after changing our meter from E7 to E10. No problems; very easy to deal with and cheaper than previous “Big 6” supplier. We had one meter that was reprogrammable but other configurations exist with more than one meter. E10 has a number of other benefits besides an extra 3 hours cheap: the cheap period in the afternoon means we now don’t need the morning or evening storage radiators (it is March!) and the add-on water timer which we have on the immersion heater is only active for 3 hours a day which, all told, saves more money.