It's difficult MikeZ but I would ask your ISP which DLM profile your on because I was hit by the change of profile when moving from BT to EE (Speed to Standard non G.INP days) happily hitting 1700 ES per day on speed then standard came in on EE and went Interleaved in 2 days and I think a DLM profile change may also happen when moving from 40/10 to 80/20.
I've asked and I'm still on speed (as it were).
Stats are slightly screwed up today because I've had to revert to the previous version of DSLstats due to 'divide by zero' errors. It appears to have re-uploaded some day-old data - that peak in ES is a red herring.
Anyway, traffic lights are all green now, so we'll see what happens...