an anecdotal update on this. Changing to the new tariff triggered a review on my direct debit payment and the upshot is that i am now paying £30 a month less than I was on the standard tariff
I think i've been using marginally less electricity since the price hike but not enough to equate to £30 a month
My only explanation is that they over estimated my usage by quite a large margin when they bumped up the price