I don't think it is IPSC at fault on Entanet.
It had a very rocky start I agree, then it settled down quite well. As I saw it most problems for months were on WBC as customers were transferred from ISPC to that.
The latest complete mess dates from the beginning of this month. Prior to that IPSC complaints were quite low frequency. Unlike WBC where the BT DLM seems considerably up the creek.
I'm firmly of the opinion which I and others have put forward in the Entanet forum that at the quarter end large reductions in IPSC (and possibly even WBC) MSIL capacity took place. And/or reductions in backhaul which would also affect WBC.
These reductions would have been triggered by bad financials at the end of the June quarter causing the financial backers to scream.
Though how many nodes Plusnet will use for WBMC and how many will be commisioned for IPSC in due course is a different question. The more nodes the more difficult the capacity planning. (I am still unclear whether multiple nodes are possible on WBMC or whether it is irrelevant).
IPSC is inevitable in the long term, but the rate Plusnet are commissioning Central capacity makes it look a very long time away. Unless old Centrals are being dropped at a similar rate.