Your E10 website is informative and excellent, thank you.
I have been on E10 in the Southern Electricity Region (20) for just over 12 months supplied by EDF.  Have today ( 23-Jan-2017) received a letter from EDF advising that the current pricing will cease on 28-Feb-2017 and new EDF Standard Variable (Direct Debit) prices will be effective from 01-Mar-2017 . This will be an 11% increase on the off-peak rate.
But as I had three months of hassle when I swapped from an arguably uncooperative SSE (Southern Electricity) to EDF just over 15 months ago, I am going to swallow this increase (as the new off-peak rate is still less than the SSE off-peak rate of 7.75p that I switched away from some 15 months ago).
The above EDF E10 pricing is provided for your info.