Sync speeds show 18xx kbps up and 244 kbps down.
The speed is going somewhere, no one knows where.
If I use BT speedtester I get full speed back on the line within a few minutes until the next router power cycle when it's back to crap speed again.
I've had numerous tickets opened with o2, their engineers are baffled too - I've lost the will to bother with it any more though.