Just to add my input I've been a Zen Business FTTC customer for 3 years. Up until 2 months ago the connection has been 100% faultless. I can't remember having a single outage.
We run our VOIP over this connection and over the last 2 months we've noticed quality issues. I've setup a BQM graph which shows some small amount of packet loss during the day which happens periodically throughout the day and night.
My Broadband Ping
Like you guys I'm getting fobbed off by their support suggesting I do some testing with a laptop plugged directly in to the BTOR modem which I will struggle to do as I'm operating a business on the connection and it's an intermittent problem anyway!
I've got a spare router the same make and model so that's my next course of action.