Looks like you may need an engineer visit.
Well BT's customer service is definitely a new level of non-existence!
They've done nothing, not even spoke to anybody from BT since this time last week and then I was promised a call back...
The DSL line continues to be unstable, one day its reporting loads of errors of downstream (scary considering I have G.INP enabled) and then its errors on upstream, then the SNR's rising and sinking....
It been a bit more stable the last 24 hours but no where near what it used to be...
Folks over at Kitz think it may be a split pair, I've done endless amounts of troubleshooting, even powered down everything but the modem to check noise noise coming off anything in the apartment and even tested other DSL equipment, cables, even tested from the entry point of the line to rule out dodgy run of cable.
I've now logged a complaint with both BT and Ofcom regarding the last 4 months of poor customer care, lies and also what might be a breach of contractual agreement.